By on April 13, 2015

premium fuel. Shutterstock user prakob

TTAC Commentator sastexan writes:

Sajeev,

I’ve been driving cars requiring premium fuel (91+ octane). When I bought my Contour SVT in 1998, high test was $0.20 more a gallon (just under a 20% premium over regular). But it was regularly always only $0.20 more. In the past decade or so, I noticed the delta going to $0.30 and even more. The correlation did not seem to be to the price (eg, premium did not seem to track a consistent 15% increase). Rather, the difference appears to be a flat rate.

Question for the best and brightest – what in higher octane fuel makes it more expensive?

What inputs are there and how much more does it cost to manufacture?

This is not intended to be a debate about the “requirement” for premium – my SVT had an extreme dislike of 87 octane and I won’t try it in my FRS with the high compression engine. However my mother runs 87 in her  with no issue for the past 5 years despite the assertion from the salesman that the “premium product requires premium fuel” and did the same for her old I30 for 14 years (Camry engine and Maxima engine, respectively).

Sajeev answers:

I’m far from an oil and gas expert, but let’s hyperlink to relevant sources and give it the ‘ol college try.

What makes premium fuel more expensive is the effort to adjust the ratio of long to short chain hydrocarbons in grades of gasoline. A notable quote from the Quora link above.

“Effectively, the long-chain hydrocarbons (like asphalt and diesel) can be broken into shorter-chain hydrocarbons (like gasoline). You end up with more gasoline. You can also adjust the regular/premium output ratios with these methods.”

Perhaps more importantly, overall fuel cost is proportional to oil quality.

Not all crude oil is created equal. The Keystone XL pipeline (that everyone’s formed an opinion about) is proof: the quality of “tar sand” oil delivered to my Texas backyard is poor. Light, sweet crude is the good stuff: more expensive as a raw material but easier to refine. But there are varying grades here too: light crude oil is “defined as having an API gravity higher than 31.1 °API (less than 870 kg/m3).” 

Whatever that means.

Need more detail? Too bad I didn’t accept that Petroleum Engineering scholarship when I was a freshman. Perhaps there’s one within the ranks of our Best and Brightest?

[Image: Shutterstock user prakob]

Send your queries to [email protected]com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

Get the latest TTAC e-Newsletter!

153 Comments on “Piston Slap: What makes Premium Fuel More Expensive?...”


  • avatar
    Sky_Render

    I run premium in both my cars (’11 Mustang 5.0 and ’14 Fusion Ecoboost). I’ve noticed that not only is premium as much as 60 or 80 cents higher per gallon now, but also that gas stations now seem to only post their prices for 87 octane. The result? It becomes much more difficult to “shop around” for a good price on high octane, since you can’t see the price until you pull up to the pump. Personally, I find this to be infuriating and a shady business practice.

    • 0 avatar

      Yes, this is annoying as you’re driving around and need to stop for gas, and I also think it’s shady business practice. I deal with the same thing because all of the stations around here advertise E10, which I don’t like to put in our gasoline-powered cars. You are psychologically lured in by the low price of the advertised fuel.

      If you have a bit of time to plan, though, I’d download the GasBuddy app, which relies on user-supplied prices for a given area. Unfortunately it doesn’t separate E10 from regular gasoline, but it does help me find diesel for my Volkswagen and can filter between regular, midgrade and premium.

      • 0 avatar
        CoreyDL

        Weird, stations here in SW Ohio usually show REG-MID-DIESEL, or REG-MID-PREM and DIESEL in a separate box. Shell stations only show regular.

        But premium gas is only 20-32 cents more than regular, and doesn’t vary much. And we have 93 here.

        • 0 avatar

          We only have 93 at a select few stations.

          • 0 avatar
            jrmason

            Elevation is one factor as to the availability of grades of fuel. Higher elevations sell lower octane fuel, my mother lives in a town that is approximately 7600 ft above sea level. Their low grade is 85 and there premium is 91.

        • 0 avatar
          cbrworm

          That’s the way it is at most stations here.

          They advertise reg-cash, reg-credit, mid-cash, mid-credit and diesel cash.

          Essentially I never know what my per gallon will be until I pull up to the pump, which is why I use GasBuddy

      • 0 avatar
        Vulpine

        I’ll agree with Kyree; Gas Buddy (and a couple other apps of which I’m aware) report gas prices at local stations around the country; these reports typically posted by people either passing a listing on the highway or visiting that specific station. These Gas Buddy listings also post when the station’s numbers were last updated, to help you determine the risk of a changed rate when you arrive. This doesn’t really require much time for ‘planning’ as Gas Buddy and the others are smartphone apps only requiring you to stop long enough to pull a map of stations near you with their pricing.

      • 0 avatar
        redav

        I always fill up at the same places, so window shopping isn’t something I do.

      • 0 avatar
        epsilonkore

        If you want non ethanol e10 gas download the “puregas” application for iOS/Android to show you gas stations that have pure petrol. That being said, get ready for a higher price (though higher performing fuel with slight, oh so slight, fuel economy improvement to slightly offset the increased price)

      • 0 avatar
        jim brewer

        The gas buddy app is pretty handy. Seems like it would be easy to include no E10 as a note.

    • 0 avatar
      DeeDub

      Use gasbuddy.com instead of windshield shopping.

      • 0 avatar
        Jellodyne

        Both the Gasbuddy and Waze app allow you to set your desired fuel type and allow you to price shop from your phone.

        • 0 avatar
          Sky_Render

          …And both the Waze app and Gas Buddy have a ton of users who simply assume that the price of 93 octane is 20 cents more expensive than 87, which is the only price advertised on the station’s sign.

          • 0 avatar
            nrd515

            Around here, with the exception of Shell, it IS almost always 10 cents more then regular for “mid-grade”, and 20 cents more for 93 “premium”. I don’t know why Shell has a giant price spread of like 60 cents from regular to “V-Power”. I don’t see any reason to pay that at all. I usually buy 93 from Sunoco or Kroger.

          • 0 avatar
            WheelMcCoy

            On a ski trip, I saw Shell had only a 5 cent difference between premium and mid-grade. That’s because at high altitudes, premium is less useful, the locals know it, and the pricing reflects that.

            There are times when you want to put a grade of gasoline in your car contrary to the guidelines in owner’s manual. Aside from altitude, if you have an old engine with carbon build-up, and the weather is very hot (like, desert hot), and the engine is pinging with regular, then you might want to try mid-grade to alleviate it.

            One time I put 93 in my Mazda3, even though the engine was designed for 87. I wasn’t after the octane. I found a gas station that sold ethanol-free gas, but it was only available in premium. Regular had “up to 10%” ethanol. Sure enough, I got at least a 10% improvement in mpg, and a seemingly peppier engine.

    • 0 avatar
      S1L1SC

      Gasbuddy – great app for shopping around. And you can set preferred grade of gasoline.

  • avatar
    mike978

    Good article. I am wondering why mid grade gasoline is sold (89) – I can see the need for regular and for premium, but who uses mid grade and why?

    • 0 avatar
      Sky_Render

      I’ve seen two engines spec out mid-grade (89 octane) fuel: the Chrysler Hemi in the early 2000s (not sure if that’s still a requirement) and the Chrysler 3.5L V6 around the same time period. I had the V6 in a car, and it had a noticeable improvement in power and response when running 89.

      • 0 avatar
        thelaine

        You are right Sky Render. My 2004 5.7 Hemi calls for mid-grade “preferred. I use premium though, because otherwise get mild knock under hard acceleration.

        • 0 avatar
          highdesertcat

          I use Premium 91-octane 10% Ethanol in all my vehicles, even if they only require 86-octane. The difference in power is noticeable and it makes gas-pedal action downright giddy.

          Even in my 1989 Camry V6 I have to use more gas pedal to get it to move with UnlRegular 86-octane then I do with 91-octane Premium.

          With the 5.7L V8s in the Tundra and Sequoia it’s no contest, while in the Grand Cherokee V6 and the Highlander V6, Premium helps goose it along.

          At my altitude, I need all the help I can get.

          • 0 avatar
            Jellodyne

            Most vehicles don’t gain any power from higher grade fuel. And at altitude you have a lower effective compression ratio, therefore your octane requirements are lower, which is why they sell 87 at sea level and 85 in the mountains.

          • 0 avatar
            highdesertcat

            Absolutely correct. In my area they sell 86, 89 and 91. Tried them all. Premium still works best for me.

          • 0 avatar
            beastpilot

            Higher octane fuels have less energy per gallon and burn slower. They’re worse fuels save one feature, which is knock resistance.

            It’s in your head.

          • 0 avatar
            highdesertcat

            Checked the pump today while filling uo the Tundra and in my area they sell 86, 88 and 91.

            The knock resistance works for me. Whether in my hgead or not, I like the performance I get on Premium 91.

            The 1989 Camry V6 had been run on 86-octane by my buddy since he bought it in 1989, and I could feel the difference immediately when I filled it with Premium 91.

            And that was not in my head.

          • 0 avatar
            CoreyDL

            HDC you’re gonna get that old Camry drunk on expensive liquor when it’s used to the Kool-Aid.

      • 0 avatar
        danio3834

        Correct, non SRT Hemis require 89 to make advertised power. I primarily run 87 octane in mine for day to day use as I’ve tracked fuel economy on both and found no difference under those circumstances.

        In theory, fuel economy should be reduced because the engine would run reduced ignition timing to mitigate knock, and this is apparent in some cars. But appearently it doesn’t matter much under every day use in this engine, it runs fine and pulls hard enough on 87.

        If HDC is running 91 octane in his vehicles that are designed for 87, the difference in performance is almost certainly in his head. If an engine doesn’t have the compression ratio or ignition mapping for the higher octane, there will be no benefit, possibly even a detriment.

        • 0 avatar
          dal20402

          Yeah, this. If a manufacturer specs 87, then running higher grades won’t do anything except burn extra cash, at least when the car is relatively new. As the car ages, compression may actually increase if deposits form on the valves. My ’87 Taurus preferred mid-grade starting around 120,000 miles for this reason.

          Both of my current cars ask for 91. The Forester XT says it’s “required” and the G8 says it’s “recommended.” I’ve put a single tank of 87 in each as an experiment. Both ran fine. With the G8, I honestly couldn’t tell any difference. With the Forester, timing was clearly being pulled as the engine was noticeably down on power, but there wasn’t any knock.

          • 0 avatar
            S2k Chris

            “Both of my current cars ask for 91. The Forester XT says it’s “required” and the G8 says it’s “recommended.” I’ve put a single tank of 87 in each as an experiment. Both ran fine. With the G8, I honestly couldn’t tell any difference.”

            Did you run a fuel economy calc? My TSX, for which premium is “recommended” gets 1-2mpg worse on 87, making it worth the “premium” for, uh, premium.

          • 0 avatar
            dal20402

            No, but I should at some point.

            The problem is that my usage of both cars is completely inconsistent between tanks, making it hard to make sense of mpg numbers. Since I don’t commute by car during the week, a tank could be made up of any mix of endless short shopping errands (14 mpg) or trips to the office on weekends (16 mpg) or trips across the city to my mom’s place (19 mpg) or road trips (22 mpg).

        • 0 avatar
          highdesertcat

          In my head or not, the Premium works better for me.

          Maybe I have carbon build-up in my engines. With 86-octane there’s a mild knock and reduced power, with 89-octane a little less of both, and with 91-octane there’s none of the above.

          Could be the el cheapo gasoline the US imports from PEMEX Mexico for my area.

          Premium seems to work real good though. Worst gas in the Grand Cherokee, Tundra and Sequoia FFV is E-85. That truly sucks!

          Never tried anything other than E-10 in the Highlander or Camry.

          • 0 avatar
            Exfordtech

            One cause of carbon buildup in an engine designed for 87 octane is the use of premium fuel in that engine. Premium fuel is effectively harder to ignite (this makes it resistant to pre-ignition) and in a lower compression engine will not completely burn, leaving carbon deposits behind.

          • 0 avatar
            SatelliteView

            I just love these “works better for me” statements to cover up one’s ignorance.

            The laws of physics work the same everywhere. A 91 octane wont do anything on an engine designed to run on 87.

            My 2.5 skyactive with 13:1 compression ratio runs identically on 87 and 91, and “no work better FOR ME” bullshit can changed that

          • 0 avatar
            highdesertcat

            I don’t sell gas but I know what I will use.

            Not selling anyone on what I use but I have tried all grades, and I am comfortable with my choices.

            I don’t need anyone to tell me what is best for me. Sounds like some libtard, greenweenie, PEV-loving agenda to say, “I use RegUnl therefore you must too, because if you don’t you’re ignorant!”

            What a crock o’sh1t!

            When we bought that 2012 Grand Cherokee new, it came with a full tank of 86-octane gas, out of Phoenix, AZ. It ran as advertised all the way home.

            But after nearly running the gas tank dry getting home, I filled it from my 91-octane stash I kept at our desert home, and it ran better, with less gas pedal action.

            No one is twisting YOUR d1ck to use Premium. Use 85 octane for all I care. I will continue to use what works best for me.

            The only BS here is the people with an agenda who think they are smarter than anyone else or whose experiences are the only ones that count or matter.

            The people who matter are the ones who put their money where their mouth is. Not the great @ss hole philosophers on ttac who can sum up their life’s resume in 25 words or less.

          • 0 avatar
            SatelliteView

            1. I don’t sell gas but I know what I will use.

            — The sky is blue, but the roads I woke on are usually paved

            2. Not selling anyone on what I use but I have tried all grades, and I am comfortable with my choices.

            — whoever questioned your level of comfort with your choice of gasoline??? But thanks for letting us know you don’t toss and turn at night when you fuel with premium

            3. I don’t need anyone to tell me what is best for me. Sounds like some libtard, greenweenie, PEV-loving agenda to say, “I use RegUnl therefore you must too, because if you don’t you’re ignorant!”

            — buddy, what you were told is that laws of physics are what they are, whether they work in your favor or not in any particular situation. You and your comfort level don’t get to decide, that should you paint your house green color the gravity inside of it will decrease.

            4. When we bought that 2012 Grand Cherokee new, it came with a full tank of 86-octane gas, out of Phoenix, AZ. It ran as advertised all the way home.

            But after nearly running the gas tank dry getting home, I filled it from my 91-octane stash I kept at our desert home, and it ran better, with less gas pedal action.

            —- it’s all in your head, but has zero bearing on REAL world. This is what people have tried to explain to you

            5. No one is twisting YOUR d1ck to use Premium. Use 85 octane for all I care. I will continue to use what works best for me.

            —- here we go again, “works best for me”. Why dont you keep repeating I’ve got $100 mil in my bank account, maybe they will appear in there if you repeat the phrase long enough?

            6. You’ll always be able to say that this method “works best for you”. You could fortify the statement by saying that you are “comfortable with this method” too….

            —- Self-projection. A very well studied phenomenon

            The people who matter are the ones who put their money where their mouth is. Not the great @ss hole philosophers on ttac who can sum up their life’s resume in 25 words or less.

          • 0 avatar
            highdesertcat

            SatelliteView, once again, it doesn’t matter to me what octane gas you choose to use.

            I know that I am not the lone ranger in my area using the highest octane gas available.

            Even people with squirrel engines in their cars and trucks who live up in the Sacramento Mountains prefer to use the 91-octane E10 available in our area.

            You must subscribe to the Jonathan Gruber school of economics and believe that all Americans who use premium gas are stupid.

            Be that as it may, I doubt you’ll change anyone’s behavior.

            I added my response to thelaine’s comment merely as info on what I use and why. In fact you must consider thelaine ignorant for using Premium as well.

            thelaine has been commenting on ttac a long time and has cred. Do you have cred?

          • 0 avatar
            SatelliteView

            1. SatelliteView, once again, it doesn’t matter to me what octane gas you choose to use.

            — OK…

            2. I know that I am not the lone ranger in my area using the highest octane gas available.

            Even people with squirrel engines in their cars and trucks who live up in the Sacramento Mountains prefer to use the 91-octane E10 available in our area.

            — So what does it prove? There are a lot of people in Russia who support Putin for his economic achievement (among other things), but it does not mean he has any. In fact, facts show that the currency has has devalued by 100% in the last year, making everyone at least twice as poor. So there can be however many 10s of millions of people who support his economic achievments, but FACTS REMAIN FACTS

            3. You must subscribe to the Jonathan Gruber school of economics and believe that all Americans who use premium gas are stupid.

            — all Americans who are using premium in an engine designed to run on 87 are stupidly wasting your money. If an owner’s manual (written by engineers) call for 91 that is a different matter. This is what you seem to fail to understand

            4. Be that as it may, I doubt you’ll change anyone’s behavior.

            —- “Two things are infinite: the universe and human stupidity; and I’m not sure about the universe.”
            ― Albert Einstein

            5. I added my response to thelaine’s comment merely as info on what I use and why. In fact you must consider thelaine ignorant for using Premium as well.

            — if his engine is designed to run on 87 with no recommendation on the owner’s manual part to use 91 – he is ignorant

            6. thelaine has been commenting on ttac a long time and has cred. Do you have cred?

            — It has nothing to do with how many times he has commented on TTAC. One can say “sugar” however many times, but the taste in the mouth wont get sweeter if one is eating an onion.

          • 0 avatar
            highdesertcat

            Yeah, I think you have drifted away from the thread “Piston Slap: What makes Premium Fuel More Expensive?”

          • 0 avatar
            Vulpine

            Right there is the crux of the matter. “— all Americans who are using premium in an engine designed to run on 87 are stupidly wasting your money.”

            However, not all engines are designed to run on 87–or rather, CAN run on 87 but are recommended to run on 91 or higher. THOSE engines very definitely do realize different performance parameters when running on lower Octane fuel. Even my Fiat 500 says “Can run on 87 Octane: 91 Octane recommended. And believe me, with a 1.4 litre engine, the difference in Octane is VERY noticeable.

            This is what you seem to fail to understand.

        • 0 avatar
          ajla

          I did an experiment last year on my old Buick equipped with the naturally aspirated 3800/LN3 by running five tanks of Chevron-branded premium through it.

          Result was zero impact on fuel economy, acceleration, throttle response, or sound.

          Unless I have a tune or modification to the engine I just follow the manufacturer recommendations.

          • 0 avatar
            highdesertcat

            Carburetor, Sequential or Port Fuel Injection?

            My brother in Palos Verdes told me ARCO has the best gas there, then Union 76, then Chevron, Shell, etc, and they all sell 87, 89, and 92 octane?

            Having been a Ford and Toyota dealer for more than 30 years, he drives an F150 4-dr 4×4 5.4 and his wife a Highlander 4×4 3.5, both using the 89-octane ARCO gas.

            But his grand sons, who love the little rice-grinder street-rod Drifters, ALL use the 92-octane for their “special-tune” four-bangers.

      • 0 avatar
        jim brewer

        Technically, my Ford 3.7L requires it because in my area at altitude, regular is 86 Ford requires 87 and makes no allowance for altitude.

        I figure that’s an inartfully written manual, but also an engine that ‘likes’ mid-grade.

        • 0 avatar
          TheyBeRollin

          You’re burning money. If you’re at a higher altitude, due to the laws of physics, you can run a lower-octane fuel. 85 and 86 will not hurt your car that calls for regular (87 at sea level).

          • 0 avatar
            highdesertcat

            A lot of people who live in our mountain country and drive small cars are also using Premium 91, primarily to eliminate that kocking, pinging and rattling as they traverse up US82 from ~4800ft to ~9300ft altitude.

            You can’t say that all those people who run squirrel engines designed to run on 86-octane are imagining things.

            What I also know for a fact is that (my assistant) Nguyen’s truck, an F150 ecobust, runs better on Premium 91.

            When he bought it new, the Ford dealership had given him a full tank of 86-octane, and it was OK but not lively enough for towing a load up the mountain.

            I know I wouldn’t put anything less than 91-octane in my 5.7L Tundra and hope to tow any worthwhile load up the mountain.

    • 0 avatar

      A good reason to use mid-grade is because you bought a vehicle that “requires” premium but you want to save a little cash. I’ve told several people with short term leases to run it, as their driving habits (tame) and engine technology can scale back timing curves accordingly.

      People like nice cars, but they don’t necessarily want premium fuel performance unless they have to. They just want the emblem, the style and the leather.

      • 0 avatar
        Pch101

        I would think that using the lower octane fuel in a car that should use premium would result in lower fuel economy, since it will operate at lower compression and therefore be less efficient.

        • 0 avatar

          Yes, but at what rate? When you are idling a big SUV in bumper-to-bumper traffic, going from 14mpg to 13mpg isn’t a big concern.

          Totally depends on the situation.

        • 0 avatar
          bunkie

          Compression ratio is fixed no matter which octane is being used. What changes is spark advance with substantial retardation thereof invoked when the knock sensor detects detonation.

        • 0 avatar
          Scoutdude

          Putting lower octane in and engine will not make it operate at lower compression. What happens depends on the engine and who made it. For most cars it will run on the same timing curve, and at the same boost levels, if turbo charged, until it senses detonation. For the majority of vehicles on the road today when it senses detonation it will retard the timing significantly for a short period of time which will result in that lower MPG and power.

          Now if it is a Ford that says premium is recommended it will actually adjust the timing and if EcoBoost, the boot level. They used the lessons learned from making FFVs with a “virtual fuel composition sensor” and applied that to infer the octane rating of the fuel. The vehicle senses a refueling event by noting a significant increase in fuel level when turned on vs the last level before it was shut off. It then goes into learning mode, trying the different timing and boost curves programmed into the PCM until it finds the most aggressive one that does not cause excessive activity from the knock sensor. It also is capable of retarding the timing on a sliding scale when it gets a reading from the knock sensor instead of pulling out a huge fixed amount of timing.

          Early knock sensor equipped GM vehicles were notorious for how much they retarded the timing when the knock sensor was activated. When the 350’s would be due for a valve adjustment that clatter would constantly set off the knock sensor and the MPG and power would suffer significantly. People were amazed the difference that a valve adjustment would work on those engines. Typically they would have had a tune up by another shop and it did not cure their lack of power or MPG. Eventually they would make it around to me and I’d say they needed a valve adjustment. Of course many would say that it doesn’t need valve adjustments because it has hydraulic lifters. I’d tell them that if the valve adjustment didn’t restore their power and MPG to come back and I’d refund the labor portion of the bill. Never had a single person who didn’t come back and say it runs better than it has in a long time.

          • 0 avatar

            Fascinating; thanks for the write-up. I’d always wondered if fuel-quality detection was an ongoing thing or if it was initiated upon refueling, so this is great.

          • 0 avatar
            Scoutdude

            @Kyree, can’t say that all mfgs do the same but you can bet if a car says premium is recommended and not required, they likely have some sort of method for inferring the octane of the fuel in the tank. Whether it is trigger by a refueling event or as a continuous monitor of course will vary from mfg to mfg. Ford though was the first and at least initially they used the refueling event to trigger octane learning.

          • 0 avatar
            jim brewer

            That sounds right. I could have sworn I felt the engine adjusting that time I filled it with E85. Guess I was right.

          • 0 avatar
            danio3834

            “They used the lessons learned from making FFVs with a “virtual fuel composition sensor” and applied that to infer the octane rating of the fuel”

            Ugh this. Sometimes the inferrence would go wonky and the controller would think it was running E85 when it wasn’t. They’d run stupid rich, it was sometimes hard to get them to relearn the proper mixture when everything *appeared* to be working correctly. Saw this on the 5.4L 3V from time to time.

          • 0 avatar
            Scoutdude

            @ Danio yeah the older FFVs with a physical Fuel Composition Sensor did not have those issues. When GM switched to the virtual FCS there were lots and lots of service bulletins on how to deal with what used to be simple procedures. If for example you had to disconnect the battery you were supposed to read the E% stored in the PCM before disconnection. Once the battery was reconnected you then need to program that number back into the computer before starting the engine. If you didn’t check the computer then you were supposed to sample the fuel and use that to program the computer. If there were driveablitly issues one of the first checks is to take a sample of the fuel in the tank and check that against the learned E%.

            The big problem with inferring the percentage of ethanol is that while it is easy to get the fuel mixture right the timing curve is also varied based on the blend and that makes a big impact on fuel economy and drivability.

      • 0 avatar
        CoreyDL

        I put mid grade in my I30 once when it had been used to premium, and it certainly did not run as well nor as smooth, though I didn’t notice a power difference. I never did that again.

        • 0 avatar
          cbrworm

          My ’97 and ’00 Maximas ran poorly on regular. They actually ran bad enough that in each case I only did it once. They said Premium recommended for maximum performance inside the gas door.

          My G35 and FX45 both say Premium fuel only. The G35 owners manual says if premium is not available, to only put enough fuel in to get to a station with premium. I think the Premium only requirement on the G35 applies only to 6MT cars, I know people with Auto G35’s that say Recommended. Unless they just randomly stick stickers on things.

          • 0 avatar
            sastexan

            cbrworm – the ’96 I30 ran great on regular, and my dad’s current G25 and previous G35 have no issues on regular.

          • 0 avatar
            CoreyDL

            I think the only way you’d think the I30 ran great on regular is if you never used premium. It did NOT like regular. At all. That VQ30 in there is smooth as butter on premium.

      • 0 avatar
        Sigivald

        One of the things I liked about the XC70 when I was shopping for cars this winter was not having to remember to tell the guy to fill it with Premium*.

        The T6 engine puts out the same power and more torque than the BMW “35” engine – and within 2hp and far more torque than the MB 3.5, and doesn’t need premium, unlike both of them.

        Makes one wonder what the design-level difference is, and why the decisions are made as they are.

        (* Oregon; I don’t get to pump my own fuel unless I’m out of state.)

    • 0 avatar
      319583076

      Until 87 octane became 10% ethanol, 89 was the only ethanol blend available here in Nebraska. Due to subsidies, 89 was cheaper than 87 and so most people bought 89. Actually, whenever the meters were visible, I noticed most stations sold more 91 octane than anything else. Now that 87 and 89 are 10% ethanol, I think 87 has become the default choice for those buying the cheapest gas.

      There are many stations around our metro that only sell two grades. I agree with Sky_Render above that it’s frustrating that you can’t tell what’s on offer and for what price without pulling into a station.

    • 0 avatar
      Landcrusher

      Most users of mid grade are people who mistakenly believe they are taking better care of their car by buying it. The refiners know this, and it’s really the only reason they sell it. In reality, this is really the biggest evil coming out of the evil oil companies.

      I say that because it’s calculated and has known negative consequences. It’s a regular bad side of both capitalism and everything else. Deny it at your peril.

      • 0 avatar
        Toad

        It isn’t evil to sell a legal product to people who demand it. If people are dumb enough to buy mid or premium grade fuel when their vehicle does not need or require it what is the evil in offering it? Customers demand the product, the oil companies provide it; it there was no consumer demand there would be no sales.

        If it is evil to sell things to people that they don’t really need our entire consumer economy would have to shut down, including most of the automotive industry. That sounds fun.

        • 0 avatar
          Landcrusher

          My main point being oil companies are no worse than other companies.

          Still, I think, and the law agrees, that sellers with more knowledge should be more responsible than just caveat emptor. This doesn’t rise to a very high bar though.

          You will find most larger companies are happy to inform you to buy the grade your manufaturer recommends, but they do so on their websites. Furthermore, since the integrateds gave up retail mostly, it’s the refiners and independents that own the stations. Exxon and Shell don’t really make much more on higher grades, it’s Marathon, Valero, and Phillips pushing the higher octane, playing games with nozzle juggling, etc.

    • 0 avatar
      S1L1SC

      My 1993 BMW 740iL calls for mid-grade. Doesn’t really like regular and I don’t see a need to run premium.

    • 0 avatar
      Vulpine

      I use mid-grade gasoline in my Jeep Wrangler. Why? Because the engine runs smoother and I realize about a 5%-10% better mileage out of it.

      Yes, I know. With some vehicles–my Jeep and my Fiat 500 notably–documentation will list a given Octane rating as “recommended”. The Jeep “recommends” 89 Octane and the Fiat 500 “recommends” 91 Octane. They both also state will run on 87 Octane. Other vehicles, especially high-performance and high-power vehicles (especially pickup trucks with the high torque engines) pretty much state, “Lower Octane not recommended.” While the computer systems on board can balance timing and injectors for the most efficient combustion possible, higher Octane fuels tend to be cleaner, burning more efficiently than lower.

      Yes, there is a whole, long argument as to the exact chemical differences and I was once told that the only difference was the addition of a “knock limiter” (i.e. some means to eliminate pre-ignition) but that exact composition really isn’t necessary to understand that just like back in the ’60s, you got better performance out of premium gasoline. However, just as running too low an Octane rating may make the engine run rougher, running too high an Octane rating may actually damage the engine by burning the valves or worse.

      With gasoline like with all other things, you have to balance the good with the bad and get what works best for you. If your car is a daily driver and you can settle for that slight performance drop, 87 Octane more than meets the need, as several above have already noted. But using the recommended Octane will likely give you the longest life from the engine.

      • 0 avatar
        mike978

        Thanks for all the answers. So is there any real detriment if they eliminated mid grade? It would free up a pump for diesel and simplify the supply chain.

        • 0 avatar
          CJinSD

          Is mid-grade actually distributed, or is it just mixed at the pump from regular and premium?

          • 0 avatar
            Scoutdude

            Midgrade is distributed to the station and stored in different tanks it is not mixed in the pump. Mixing in the pump is a relatively new (again) phenomenon now billed as “blender pumps” that allow you to select different blends of Ethanol with typically E10, E85, and one or two intermediate blends.

            I say that the blender pumps are new (again) because they existed back in the late 60’s and 70’s at some Sunoco stations. They had a dial and you could dial the octane that was desired. Don’t know how they handled the pricing back in the day of mechanical meters, I was too young to drive but I remember seeing those pumps watching the family car being filled by the attendant.

          • 0 avatar
            dtremit

            @Scoutdude Found this gallery of one of the old Sunoco pumps here: https://www.flickr.com/photos/dakelm/sets/72157627051475679/

            Looks like it wasn’t a continuous adjustment, but up to 9 different blends — and it had a separate price for each. What a pain that must have been to configure.

            Interesting to note they had a grade below “Regular,” back then — something which Sunoco continued until fairly recently in a lot of locations. They had “Economy” (which was 86 octane in 87-octane areas) below “Regular.”

        • 0 avatar
          Landcrusher

          There was a reasonable need for it when we switched from leaded fuels. Many older engines would get less knock from upping octane.

          Now, apparently, cars are speccing it. That all said, you could get rid of it anyway. I doubt you would save though due to volume sold being sufficient.

          Now that most retailers are not owned by the integrateds, and not even by refiners, the retailer is the real decision maker and they make the most off of it. I don’t see it going away.

        • 0 avatar
          Pch101

          Midgrade is produced at your local gas station by blending premium and regular.

          • 0 avatar
            mike978

            That would make sense – thanks.

          • 0 avatar
            Scoutdude

            No midgrade is not typically mixed at the pump it is delivered to the station in the truck and stored in a separate tank. If pumps that blended it on site were readily available then Costco and Sam’s Club would not only offer Regular and Premium to avoid having as many tanks as they do. Next time you pull into a station look at how many of the fill points are in the lot. That corresponds to how many tanks are in the ground.

            Here is a link to a distributor that sells midgrade to stations. http://www.jbco.com/fuels.php

          • 0 avatar
            Pch101

            The grades are blended together at the pump — not unlike the way you’d blend gin and vermouth to make a martini — producing a kind of octane cocktail. The precise proportion in which the grades are blended determines the octane of the gas that enters the customer’s tank.

            This feat of gas pump bartending is performed by something called a blend valve. This valve has inputs consisting of two grades of gasoline, each from different tanks. A single, moveable barrier called a shoe is connected to both in such a way that it can be moved across the inputs with a single motor-driven ratchet. As the ratchet opens one valve, it closes the other valve in precise but opposite proportion. This means that when one valve is, for example, 90 percent open, the other valve is 10 percent open, creating a mixture that consists of 90 percent of one octane and 10 percent of the other. By shifting the ratchet back and forth, the blend valve can produce any octane of gas, ranging from the highest to the lowest grades stored in the tanks — and all octanes in between.

            http://auto.howstuffworks.com/gas-pump4.htm

          • 0 avatar
            Scoutdude

            Sorry PCH but those blender pumps are relatively new and the majority of pumps out there are of the old type being fed from separate tanks.

          • 0 avatar
            Pch101

            Blender pumps have been around for years.

          • 0 avatar
            Sigivald

            Every source I can find says that blender pumps are commonplace (but not universal) for mid-grade – what’s new(ish) is using them to add in ethanol.

            So Pch is right, and Scout is right about the Ethanol aspect.

            Reading downthread, I see Scout also seems to use “blender pump” to mean one where the USER can select the ratio; Pch – I assume – and I are referring to one that does a fixed-ratio blend internally.

            (I suspect station age is the biggest factor; older stations will almost certainly have three tanks and not blend.

            A new station – or an old one that was replacing tanks – would be foolish to not consolidate tanks and avoid inventory issues by using a blending pump.)

          • 0 avatar
            Scoutdude

            @PCH it has only been about 5 years since the modern blending pump was introduced so the majority of pumps still in use are not blender pumps. If a station is new or has had its tanks and pumps replaced in recent years it MAY or may not have blender pumps. Virtually every jobber will sell mid grade to the stations they serve, though they may blend in the tanker.

          • 0 avatar
            Pch101

            I have no idea where you’re getting this “five years” thing from. The pumps have been around for decades.

            As noted, what is new is the ability for pumps to do ethanol blending. Blending for octane is nothing new.

          • 0 avatar
            Scoutdude

            @PCH they were around decades ago at Sunoco stations which was a Wayne pump that was unique to Sunoco stations. It is only recently that other mfgs started making blending pumps and were able to sell them to whoever they wanted.

            “Sunoco is the only major gasoline retailer to sell four grades of gasoline in the U.S., due to its proprietary pumps which blend regular with Ultra93 to obtain the mid-grades” Note the proprietary part.

          • 0 avatar
            Pch101

            Note the number “four.”

            Most gas stations sell THREE grades of gas.

          • 0 avatar
            Scoutdude

            Another tip look at the pump at your local station if there are separate hoses and nozzles for each grade then each grade is stored in different tanks. Most of the pumps that are at stations that are/were branded with Texaco, Shell, Mobile, or Circle K still have those types of pumps around here.

            If the pump has a single hose it may or not be fed by different tanks for all 3 grades.

            Fact is that blender valve is not as simple as changing the position of that shoe to a given location to ensure that there is a desired percentage of each fuel delivered. Flow is a complex subject and differences in the length of each supply line, depth of fuel in each tank at a given time ect will affect how the flow rates through each side.

        • 0 avatar
          Sigivald

          Well, people with the small number of cars that require mid-grade would have to run premium (or under-grade and run regular).

          Plus, diesel needs a new nozzle and such anyway, and lots of places already *have* it…

      • 0 avatar
        Scoutdude

        No running higher than needed octane will not damage an engine, lower than needed octane on the other hand could damage engines before the advent of the knock sensor.

    • 0 avatar
      redav

      When I owned an older car, I noticed it started to knock. I used midgrade to fix that until I got the cause sorted out (cleaning the engine to reduce carbon build-up seemed to do the trick).

      The old advice was always use the lowest octane necessary to prevent knocking, and if you didn’t need premium but regular wasn’t enough, bam! midgrade.

      • 0 avatar
        JMII

        My older Ranger required mid-grade to eliminate knock while towing. It would run on regular (87) just fine around town, but towing on the highway required mid grade (89). My current Dakota doesn’t have this problem. My other vehicles require premium (93). I think they only require 91 but 93 is what is available at most stations.

  • avatar
    Eric M

    Octane rating is not just a function of chain length, is is also a function of isomer composition. In hydrocarbons the chains are not always the pretty straight lines of carbons in the graphic, they are usually branched a bit. If one holds the number of carbons constant, a hydrocarbon that has more branches will usually have a higher octane rating. Additives are a big factor too, as some can really goose the octane rating.

    As for what we call ‘octane’. The definition of 100 octane is 2,2,4-Trimethylpentane (a.k.a. iso-octane, highly branched 8 carbons). While n-heptane (a straight 7 carbons) is the zero octane standard.

    As for cost, I’m sure at least some of it is just that people will pay it. But some of it will come from extra processing to get all those branched hydrocarbons in there (and straight chains out).

    • 0 avatar
      sastexan

      Has the cost of that extra processing gone up, or have the oil companies figured that they can charge an additional premium for a perceived premium product?

      • 0 avatar
        Scoutdude

        The companies have figured out that they can charge more. I used to work at a station when I was in college and I worked Sun night when our weekly delivery happened so I got the bill. At the time Premium cost less than a dime more than Premium and this was back when regular was in the just over $1 range in our area. Regular was priced at invoice, all profit was from the rebate, Premium was priced a flat 20 cents more. Now as the price of crude has gone up significantly it does not surprise me that the spread between the two have increased along with it has not increased at the same percentage as has the price of fuel. That said I’m certain that most stations make more money on a per gallon and on a profit margin percentage on Premium vs Regular.

        • 0 avatar
          SatelliteView

          I thought the price of the crude has gone DOWN significantly…

          • 0 avatar
            danio3834

            I guess people really do have short memories when it comes to stuff like this.

          • 0 avatar
            Scoutdude

            @ SatelliteView reread what I wrote, I was in college gas was around $1 per gallon, it has gone up significantly since then yes it has recently gone down significantly from the peak but it is still significantly more that $1 per gallon for retail gas.

        • 0 avatar
          SatelliteView

          $1 in 1990 is $1.80 in 2015 What’s the cost of regular on average today, $2.40? So a 25% increase over 20-30 years is not significant at all

          • 0 avatar
            Scoutdude

            Buying power or the rate of inflation has nothing to do with this discussion. It is all about the absolute price and the relative price difference between regular and premium. In 1990 Premium was about 6% more expensive to the retailer but they charged about 20% more at retail and that 20% difference was due to a 20 cent per gallon difference which was universal in my area at the time. Now that price difference is not universal I still see some places with that 20 cent per gallon spread while other places have a 30 cent per gallon spread in my area. At current prices in my area a 25 cent per gallon price difference is slightly more than 10% in my area.

            Since I don’t work at a station now nor know anyone that does the question is how much more the retailer pays for Premium than regular in either cents per gallon or as a percentage.

  • avatar
    redav

    “Light” and “heavy” crude is exactly as described–it has to do with the density (and thus primarily the size/type of the carbon chains). Light oil is already closer to being fuel so it requires less refining. Heavy crude is closer to wax or asphalt (i.e., sludge) and so requires more processing to turn into fuel.

    “Sweet” and “sour” refer to the sulfur content. Sour oils have H2S, which is a very nasty chemical. Sweet oil does not. Sulfur has to be removed during refining, so that makes sour oil less desirable (cheaper). Also, the difficulty of removing enough sulfur to pass ultra low sulfur requirements is one reason that diesel increased in price.

    Different locations have different types of crude. As well-known, west Texas has light sweet crude, while Venezuela has heavy sour crude (which few companies can extract and few refineries can process).

  • avatar
    Pch101

    The basic reason for the price spread between regular and premium is the additional refining required to produce premium.

    The OP’s question is why is the spread increasing. But it isn’t increasing — the spread in percentage terms has been declining since the 1990s: http://www.eia.gov/todayinenergy/detail.cfm?id=11131 The EIA attributes that decline to the increased use of ethanol, as ethanol acts as an octane booster that in turn allows refiners to produce a lower grade of gasoline.

    • 0 avatar
      sastexan

      Perfect graph, that’s info that I thought would support my hypothesis, although it appears to counter it. I think the spread is a lot larger than this graph shows. Maybe in the DC area the oil companies think they can soak the so-called “rich” more than in other places?

      • 0 avatar
        Pch101

        The EIA is an authoritative source for US gas prices (and for energy data in general.) I would trust their data.

        • 0 avatar
          Scoutdude

          But that data is aggregate data and at the local level things vary. I know there are stations around here that do typically still have that traditional 20 cent spread and others that have a 25 or 30 cent spread. The interesting thing is that many of those stations with the higher spread still have the traditional 10 cent spread between mid grade and regular. Not surprising many of those stations with the higher spread are in more affluent neighborhoods.

    • 0 avatar
      Sky_Render

      If the spread “isn’t increasing,” then explain to me why my local gas stations all of a sudden started charging me 60 cents more per gallon for 93 octane.

      • 0 avatar
        Scoutdude

        As I mentioned above the data that PCH linked to is aggregate data and in no way reflects what happens in a given area. So I’d say the gas stations in your area have figured out that they can make more money overall at that price. Sure they probably scared away the people who like to buy it but that is offset by those how have to buy it. Sell 10 gallons at 20 cents per gallon profit or sell 5 gallons with 50 cents per gallon profit.

        Also note that the portion of the data that PCH was quoting was based on percentage difference and it is old data that doesn’t reflect the recent drop in prices.

        • 0 avatar
          Pch101

          Exceptions don’t prove the rule. Exceptions are, by definition, exceptions.

          There’s a gas station down the street from me that consistently charges $1 or more per gallon more than everyone else. It is a total statistical outlier and does not reflect the averages, and its existence in the marketplace has no meaningful impact on the averages. If I want to have a feel for the overall gas market, it is one place that I would exclude because it is such an oddball.

          And if you follow the EIA data, then you will know that it provides regional data in additional to the national data. AAA also provides it at a local level, and you will find that EIA and AAA data are quite similar to each other.

          It isn’t wise to rely on gut feelings. There’s plenty of data: use it.

      • 0 avatar
        slance66

        My theory on the spread, based solely on observations is that in areas with a lot of luxury (German mostly) cars requiring premium, stations jack up the spread knowing they have customers who will pay it. My area is heavily concentrated with such cars and the spread is close to 50 cents. Traveling within the state last week, venturing to a more blue collar area, the spread was 20 cents.

        When we still had Sunoco stations selling 91, I could at least save a nickel a gallon over the cost of 93.

  • avatar

    Similarly, Mister Mehta, what do you think of using premium fuel in luxury cars whose engines are shared with more-plebeian cars? I understand putting premium-fuel in an LS 460 since that is a Lexus-specific engine, but the ES 350 and RX 350 share their engines with—among other things—the V6 Camry, and don’t seem to drive all that differently. So when the Lexii specify premium fuel while their Toyota-branded brethren do not, should you heed the labeling? Are the Lexus engines tuned differently?

    • 0 avatar
      TrailerTrash

      True!
      These makers all seem to use the same 3.5 in every car they make from low to premium and the gas requirements all change.
      Same engines…different octane.
      Wonder why???
      Good question.

      • 0 avatar
        hybridkiller

        “Same engines…different octane.
        Wonder why???”

        Engine displacement doesn’t include the combustion chamber that’s in the head, so different head design = different compression ratio – same displacement.

    • 0 avatar
      psarhjinian

      In the case of the Lexuses, the engines are tuned differently and use a different injection system. So yes, you’d be best to use premium fuel in them.

      I can’t speak for the VQ V6 in Infiniti’s products, but I assume it’s the same. If nothing else, you usually take a hit in performance and/or fuel economy.

      • 0 avatar
        CoreyDL

        The VQ engines in (at least some) Infiniti products are different, with higher compression. They are known as the VQ-HR series of engines (High Revolution).

        • 0 avatar
          danio3834

          The 4.0L version in the Frontier recommends premium for advertised power as well. How many small pickup buyers are ponying up for that?

          • 0 avatar
            CoreyDL

            I’m not a big fan of that VQ40. It’s loud and coarse, doesn’t provide big power, but drinks (apparently premium!) fuel at the rate of a hemi V8.

            This has been the experience of my parents with a VQ40 Pathfinder.

            They should just use the 3.5, it is better in all ways.

          • 0 avatar
            bball40dtw

            “How many small pickup buyers are ponying up for that?”

            Just the Australian ones, but I think the pony up for the diesel instead.

        • 0 avatar
          sastexan

          I should have also mentioned that my dad has used regular in his past two Infinitis (one of the first G35s off the boat and his current G25). I don’t remember if he used regular in his J30 before it was totaled by a Suburban and a Jag XJ sliding into him at a stoplight.

          I am not sure if his mileage is better or worse – but he only gets 21 or so in his G25, all city / urban driving with AC on (Texas), lots of short trips.

      • 0 avatar

        This.

    • 0 avatar
      Pch101

      All things being equal, higher compression engines require more octane. The hybrid versions of the Lexus RX have high compression gas engines, hence the need for premium.

      • 0 avatar
        Scoutdude

        The compression ratio of the Toyota and Ford Hybrids is overstated because they work on an Atkinson type cycle. The CR is calculated in the normal manner which compares the swept volume to the combustion chamber size. In the engines that operate on the Atkinson like cycle the intake valve has a delayed closing forcing some or much of the charge back out of the cylinder. The Prius has a high advertized CR but does not require premium nor is it recommended.

    • 0 avatar
      sastexan

      Somehow the model of the Lexus was left out of the article – my mom has an RX350 (non-hybrid), and the engine has virtually the same power as the camry / highlander. I assumed the differences were due to intake / exhaust packaging more than anything, not tuning.

      And yes, she has run the car successfully for 5 years / 34k with no issues on regular Costco/Sams club gas (with some Racetrack thrown in there sometimes, as well as whatever else is cheapest). Her old I30 was the same – 14 years and 97k on regular. Only engine repairs (if you can call it that) on that car was all three O2 sensors around 65k.

      • 0 avatar
        Sigivald

        Edmunds says the RX350 uses regular, not Premium, and the owner’s manual agrees, saying 87 octane.

        So … yeah, no surprise no issues; it’s factory recommended.

        • 0 avatar
          sastexan

          Sigivald – nope; the manual for her 2010 says “Octane rating 91 (Research octane number 96) or higher”.

          http://drivers.lexus.com/t3Portal/document/om/OM48B58U/pdf/sec_06-01.pdf

          • 0 avatar
            slance66

            It changed in 2013 I believe. Our 2007 takes 91. Of course, only Sunoco even sells 91, and it’s not gone locally.

  • avatar
    bikegoesbaa

    Selling price (of anything) is unrelated to the cost to manufacture.

    Premium costs more because:
    1) For some buyers it actually provides additional real utility/value over lower grade fuels
    2) Many buyers who do not understand how engines work erroneously believe that it provides them with additional utility/value even though it does not

    Selling price is determined by what the product is worth to somebody, not what it cost to make. Are you willing to pay me extra vs my competitors just because I have an inefficient, expensive manufacturing process? I hope not.

    Cost to manufacture determines the price at which something can be sold *profitably*. But people won’t buy things if that price exceeds the actual value of the item to them.

    GM knows all about this, that’s why they sold cars at a loss for 20 years.

    • 0 avatar
      Pch101

      From a refiner’s standpoint, premium gasoline isn’t an essential component of refining — the fuel is only offered because some people want it.

      It genuinely costs more to produce premium. If producers couldn’t pass on the higher costs, then they wouldn’t bother to refine it at all.

      • 0 avatar
        Scoutdude

        That is true at the refinery level but once it gets to the retailer they are free to charge a higher profit margin on the Premium if they feel they can get it and some certainly do.

    • 0 avatar

      “GM knows all about this, that’s why they sold cars at a loss for 20 years.”

      It’s also how they can sell Yukon Denalis for well over $70K all day, unfortunately.

      Hey, do those take premium? I’m pretty sure they have the larger 6.2-liter V8 from the Escalade.

      • 0 avatar
        bikegoesbaa

        “It’s also how they can sell Yukon Denalis for well over $70K all day, unfortunately.”

        I don’t know that this is unfortunate. They can charge top dollar for those trucks because buyers think they are worth the premium.

        I’m not a fan of that sort of vehicle, but I don’t see a problem with GM getting the most that they can for them.

  • avatar
    TrailerTrash

    long time ago…they took away lead. they charged more and told us because now that they were not putting in lead, they needed to charge more for taking it out.

    Um…OK.

    Now they force me to use alcohol and charge me for it…but this takes away power and causes me to use more gas.

    Um…OK.

    Again.

    And the cost of food is more as well because, well…now we are burning it in our cars so we can spend more on gas. I know I am living in a Lewis Carol world when I am burning my food for gas.

    • 0 avatar
      Drzhivago138

      Educate thyself.

      http://en.wikipedia.org/wiki/Food_vs._fuel

    • 0 avatar
      DC Bruce

      Actually, tetra ethyl lead was added to gasoline as an anti-knock compound, i.e. raising its octane rating. When lead stopped being added, the refiners had to brew a gasoline that had a higher “native” octane rating in order to maintain the same anti-knock properties. The volume of tetra ethyl lead blended in gasoline was miniscule, so there was no effect on fuel economy.

      The need for a higher native octane rated gasoline is why it cost more once the lead was removed. Alcohol also is an anti-knock compound, so that reduces the need for a higher native octane rating of the gasoline blended with it. The downside is that alcohol is less energy dense by volume than pure gasoline, so a blend of alcohol and gasoline has less energy in it than the same volume of pure gasoline, resulting in poorer fuel economy.

      There should be no effect on the power of the engine, assuming that octane rating of the blended fuel meets the engine’s requirements.

    • 0 avatar
      Sigivald

      They (the State) took away lead because it was kinda very poisonous.

      And it cost more to replace it because tetraethyl lead was *an octane increaser*, and they (the fuel companies) needed to keep the octane levels up to prevent your (your) engine from destroying itself, since there were no knock sensors to speak of in 1973, when the phase-out started.

      • 0 avatar
        TrailerTrash

        I did not know they replaced the lead with more expensive additives. I know they always work to improve the gas with additives and such, just not that substitution for lead was one reason.
        I do know all our boats are having tough times with the booze. We go long distances for stations with food free gas.

  • avatar
    George B

    Sajeev, premium gasoline has a greater proportion of more complex branching hydrocarbon molecules, isomers, that burn in a slower and more controlled manner. The simple straight hydrocarbon molecules, think paint thinner, burn in a way that causes engine knock while the molecules with branches can handle higher compression ratios without engine knock. The refinery process requires extra catalyst steps to make the more of the desirable branching isomers.

  • avatar
    Frylock350

    I primarily burn E85 in my Silverado and its a wonderful fuel, minimally 100 octane. I take a fuel mileage hit of about 18%, but the fuel is cheaper so it makes up for it ($1.99 for E85 vs $2.69 for 87 octane this morning). Chevy claims a 25hp increase as well as slightly large torque bump as well. These differences are very noticable; objectively Lingenfelter claims E85 takes 0.5 seconds of the 0-60 sprint.

    • 0 avatar
      Sky_Render

      The problem with E85 is that in most places I’ve been, it’s only 20-30 cents cheaper per gallon than 87 octane. At that small price differential, you LOSE money by using E85. (E85 gives roughly 30% less fuel economy than gasoline, so if E85 isn’t 30% cheaper or more, you lose money.)

      • 0 avatar
        Scoutdude

        No E85 contains 30% fewer BTUs than pure gas but in the real world because of the higher octane and the FFV’s ability to adjust the timing curve the resultant loss of MPG is typically in the 15-20% range.

        • 0 avatar
          Sky_Render

          The gubment would like to disagree with you:

          https://www.fueleconomy.gov/feg/flextech.shtml

          That states that the reduction in fuel economy CAN be as high as 30%.

          However, we’re arguing over semantics at that point. My original point was that unless E85 is SIGNIFICANTLY cheaper than 87 octane, it costs you more money to use it. Here’s an Edmunds test with a Chevy Silverado that illustrates this:

          http://www.edmunds.com/fuel-economy/e85-vs-gasoline-comparison-test.html

          TL;DR: $125 in 87 octane vs $155 in E85.

          • 0 avatar
            Scoutdude

            The reality is that for most areas what is sold most of the year as E85 is actually E70. CA and NV have the greatest amount of time that E85 is actually E85 so they almost certainly using true E85 and their loss in MPG was not 30% it was only 26%. If you are in an area where it is common to have overnight lows 60 degrees or less in a given time of the year you do not get E85 that time of the year. You often end up with the time before the switch to full E85 being drawn out to use up stocks and the time that they switch back to intermediate or winter blend to start a little eary to ensure that people aren’t stuck with too high of a blend. E70 has been show to be the point where the economy starts to drop off significantly.

            Of course the results vary from car to car and driver to driver so each person must figure out the break even point for themselves rather than going purely by the difference in BTU content and what the gov’t requires to be posted on the window sticker.

    • 0 avatar
      Scoutdude

      If you have blender pumps in your area try putting in E40 or E50. Back when we had a Taurus FFV I’d use E85 when it was priced right but I also ended up blending a bit because I’d fill before empty due to a good price. At somewhere between E40 and E50 the MPG was about the same as E10 so the cost savings increased. There have been a number of studies using different vehicles that showed that the relationship of ethanol to MPG was not linear. For most vehicles it dropped as Ethanol percentage increased to somewhere in the 25-30
      % range, then the curve took a turn and somewhere in the 40-50% range it would peak before starting to fall again. After E70 the drop off increased dramatically. Note in many areas the stuff sold as E85 is actually E70 for most of the year. The actual blend depends on the expected ambient temps for the season.

  • avatar
    CB1000R

    And if you ride amotorcycle that needs high octane, try to use a pump with separate hoses for each grade. Single hose will hold a bit of the previous customers selection. So I’ve always been told.

  • avatar
    strafer

    Back in the 80’s when I worked at my dad’s full service gas station, I did the paper work among other things.
    Back then the difference between the grades were only 2-3 cents, but we and all other gas stations charged a dime more per grade.
    You may remember how plus was 10 cents higher than regular and premium 10 cents higher than plus (mid-grade).
    And full service side charged another 10 cents on top.
    But selling gas did not make any money, it was just a front to bring in customers for car repair, rent U-Hauls, etc.

    • 0 avatar
      Scoutdude

      That is the way it was when I worked at a station when I was in college. Regular would be priced at invoice, Mid grade at invoice plus 6 or 7 cents, premium at invoice plus 12-14 cents. That is not to say that regular was priced at cost because there were rebates/discounts based on monthly volume which would result in 2-3 per gallon off of the final price paid at our low volume.

      Full serve was an extra 10 cents but that was pretty rare, if I’d get one car in on my shift per day that was unusual. The owner had a minimart station right next door so we mainly existed to handle overflow, those that had a Texaco card instead of a Mobil one, and so the owner had a place to take his cars for service and repair. I think the other reason was so that it didn’t seem to the public that he had the monopoly that he did on gas sales in that area. He had lots of minimarts that carried his name and the Mobil brand but there were almost as many full service stations or car wash/gas stations that did not carry his name with Texaco or Arco sign out front in his portfolio. He also owned the Mobil bulk oil distributor in town so if you bought gas at a Mobil branded station or an unbranded station in the area you were probably putting some money in his pocket.

    • 0 avatar
      Truckducken

      Same concept still applies: http://www.eia.gov/dnav/pet/pet_pri_refmg_dcu_nus_m.htm

  • avatar
    DIYer

    Supposedly motorists are using less premium gas today, so the refineries are producing less of it. To make up for less sales of premium, they charge more.

    http://blog.gasbuddy.com/posts/-Grade-Gap-widens-as-consumption-of-premium-drops/1715-516615-1407.aspx

    Gas price down the street: $2.12 regular, $2.32 midgrade, $2.52 premium

  • avatar
    55_wrench

    Great discussion here.

    Engine management controls have been improved to a great degree over the last 10 years or so..to the point that I haven’t heard any preignition or spark knock in anything I’ve driven in that interval.

    We bought a gently-used LS430 late last year and loaded it up with a trunk full of luggage, the two of us, and more stuff in the back seat- probably 500 lbs total payload-and took it on a 4000 mile road trip.

    The difference between using mid grade and 89-91 octane was impressive. The high octane gave the best overall throttle response, and the best mileage as well, 26MPG at posted 75-80 MPH speeds. And that was leaving Central Texas and coming uphill against the Continental Divide.

    I’ll run midgrade around town, but it gets the good stuff anytime we take it out on the highway.

  • avatar
    mr_min

    Sajeev

    My memory is a bit hazy on this but once upon time, I meet with the oil boys and fuel production was described to me as a piece of cake/pie with the raw oil as the whole pie.
    Each barrel of oil as a certain amount of energy and can be cut into different ratios of the key products.
    For example 1 Barrel might be split like this
    30% Jet A
    30% Diesel
    30% Reg Gas
    5% Premium
    5% other products
    These ratio are hard to change quickly, and are dependent on the raw oil source.

    The Premium fuel requires more complex processes and costs more to produce (more energy input to crack the product), and takes away from cheaper to products.

    Refinery typically want to constraint supply of low volume products to a minimum to avoid over supply and maximize profit on the high volume easier to produce products.

    http://www.aip.com.au/industry/fact_refine.htm

    my 2c worth..

    • 0 avatar
      jrmason

      The percentages of gas-diesel are quite a bit different with the oil refineries in the US. The typical US refinery averages approximately 12 gallons of diesel fuel to 19 gallons of gasoline out of a barrel (42 gallons) of crude. This isn’t a rock solid number but there is almost always a substantial gap between the 2 fuels being refined for various reasons.

    • 0 avatar

      Does this percentage of products per barrel vary significantly between different grades of oil? That is, between two extremes like sweet crude and tar sand oil?

      • 0 avatar
        Scoutdude

        Yes it does. Ultimately a refinery would love to use straight distillation to produce their products and the ratios of the different products will vary based on the input crude. However the demand does not match what is derived from straight distillation so they use more complex processes that cost more to shift the ratio of products to meet demand. Note depending on the ratios desired that 42 gallon barrel of crude can produce more than 42 gallons of finished product though some of that is due to additives.

      • 0 avatar
        mr_min

        My understanding is yes it does.

        My understanding is that older refineries are typically set up to refine a particular crude.

        In Australia most of the refinery are small and 30yr old, and were set up to crack sweet light crude. They would require upgrading to process Sour heavy crude.

        I learnt this in the context of increasing passenger and light commercial diesel, which the refineries advised was affecting the ability to supply premium gasoline and JetA in Australia.

  • avatar
    jdogma

    The article does not explain that straight chain (aliphatic) hydrocarbons longer than 4 carbons are very bad with respect to octane rating. For instance, butane (4 carbons) has a motor octane rating of 114 (gasoline has to be made from mostly longer chained molecules to keep the boiling point reasonable), the next in the series, n-pentane (5 carbons), has a motor octane of only 66. Branched chain and cyclic hydrocarbons have good octane numbers, but these are made by catalytic reforming, which is more expensive than the cracking + distillation methods used to produce the straight chain analogs. Cyclopentane (produced by catalytic reforming) for instance has an octane of 141. The high octane hydrocarbons are more expensive to produce than the low octane constituents.

Read all comments

Recent Comments

  • Inside Looking Out: @slavuta: You become famous!
  • Inside Looking Out: It is hilarious. What a bunch of idiots, do they really think everything is/will be under their...
  • slavuta: your fits don’t change anything. Yuri Bezmenov warned us, one day Americans will look at black and...
  • sgeffe: You probably have a point there!
  • sgeffe: Shark! Jumped!

New Car Research

Get a Free Dealer Quote

Who We Are

  • Adam Tonge
  • Bozi Tatarevic
  • Corey Lewis
  • Mark Baruth
  • Ronnie Schreiber