By on October 1, 2007

texpump.jpgWhat Car? [via The Daily Record] says premium petrol is a rip-off, providing neither extra power nor superior gas mileage. The UK consumer magazine paid a lab to test various premium grades against their lowly counterparts. The lab concluded that premium petrol purchasers may eke out a few more miles to the gallon, but the cost (up to 30p more per gallon) outweighs the benefit. In specific, they claim that Shell's V-Power petrol couldn't quite match the mileage provided by regular: 22.9mpg to 23mpg (which is well within the margin of error). The article fails to mention that certain car manufacturers require premium unleaded for a reason; the knock sensor will smooth things over, but you'll get pitiful gas mileage and probably damage your engine over the long run. 

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31 Comments on “Premium Gas A Con?...”

  • avatar

    I lent my A4 to a friend who filled it up with regular before returning it back. Near the end of the tank when I was driving it, it started to smoke like crazy and have almost no power. If a manufacturer tunes a car for premium, you use premium. You can’t just decide to downgrade regardless of what anyone says about the gas.

    This article doesn’t say if they studied the effects of premium vs. regular and desposits, emmissions (only noted in a BP study), etc.

  • avatar

    This must be a UK thing… I’ve never seen premium advertised in the States as providing better gas mileage. Granted, your average American driver still doesn’t know about detonation and knock sensors, but they know that some cars need premium, most cars don’t, and they have no idea why. Nobody I know thinks that higher octane gas gives you better mileage.

  • avatar

    The Daily Record’s article is completely useless as it didn’t even identify the car or cars that they used in their comparison!

    It’s probably been said here many times before, but premium gas is only useful for engines designed to utilize it effectively, or engines that have been retuned (“chipped”) for performance. But for those cars for which it is useful, it is often quite necessary.

    Premium contains more octane, which is a combustion *retardant*. Premium burns at a slower rate than does regular gasoline. High-performance engines take advantage of this fact in their design and operating parameters.

    Take the LS2 engine with it’s 10.9:1 compression ratio. The use of regular gas can cause preignition. Sure, the computer can compensate by retarding the ignition timing, but performance (and gas mileage) can take quite a big hit.

    Premium is *not* a “con”. There are cars that use it (and need it). Most don’t. Then again, I had a 1981 Ford Escort that complained vociferously whenever less than 92 octane was put in!

  • avatar

    Two types of cars need premium gasoline. High-compression naturally aspirated engines and engines that use an external means of increasing compression (turbos and superchargers).

    When you squeeze a fuel-air mixture, it becomes more volatile. That phenomenon is the entire basis of a diesel engine. The fuel-air mixture is compressed until it explodes – an external ignition source is not necessary.

    The same thing happens in a non-diesel engine if the fuel does not resist this. The end result is fuel detonation at the wrong time…..very bad for your engine. Detonation kills performance and fuel economy.

    High-octane fuel resists premature detonation at higher compression. This allows an engine designer to extract more performance from an engine (high compression engines typically make more power than low-compression engines).

    Don’t run cheap gas in a high-compression engine. You paid for a high-performance motor; spend a few dollars on the right fuel.

  • avatar
    Johnson Schwanz

    I use midgrade unleaded (89 octane) as a nice compromise. Octane tolerances may abound, so I take the middle road.

  • avatar

    I thought it was common knowledge that Ford sourced the ’81 Escort engine from Ferrari. It may have even said HO (High Output) somewhere on it.

  • avatar

    I noticed the source failed to report was that not only are these premium fuels more refined (Hence, they burn better) but they also have far more detergents that regular and clean your fuel system and engine better. BP Ultimate also has a rust prevention treatment which can stop rusting of the fuel system, including the fuel tank. Over the course of the life of a car, this could keep the car in better shape than regular.

  • avatar

    Many people think that premium gas has more energy content than regular and they will not, in my experience, believe otherwise. It’s just something they heard.

  • avatar
    Sajeev Mehta

    And even a knock sensor can’t save a forced induction engine (turbo/supercharger) that’s consuming regular gas.

    Pretty flawed article, but it holds true for a majority of late-model cars, since their timing curves are low-octane friendly.

  • avatar

    I’ve got 80k on a 2002 BMW X5 3.0 with a 5spd (yeah I was the one that bought it with the manual box). Premium (91) is the recommended octane according to BMW. With my wife driving her normal weekly commute to work, we see about 23mpg average on a tank. Just for comparison’s sake, we tried 89 octane (mid-grade) and the average dropped to 19. Same person, same driving, same commute.

    4 mpg x 24 gallons (tank)= roughly 96 miles
    96 / 23mpg average = 4.173 gallons x $3.35 for premium fuel = $13.98 per tank

    Cost to fill up 24 gallons at $3.35 (91oct) = $80.40
    Cost to fill up 24 gallons at $3.25 (89oct) = $78.00

    Difference in fuel costs = $2.40 per tank
    Difference in usage = $11.58 per tank ($13.98 minus the $2.40 difference)

    Hence, for us (I know, small sample) using 89 octance fuel is a false economy. Maybe the 3.0 motor is extraordinarily sensitive to octane. I’m not trying to make blanket statements about ALL cars, but saying that for our X5— premium pays for itself.

  • avatar

    Engines with higher compression ratios that have been designed for use with higher octane fuel need premium gas.

    However, for all other engines, premium gas is a waste of money – it generates neither power increase nor better mileage. As to the advertising hype about so called cleaning agents – all gasoline sold in the US has detergents in it that keep the fuel system clean – they are mandated via federal standards.

  • avatar


    CarTalk recently published a letter about the varying quality of detergents in different brands of gas. The quick summary is that in 2004, several automakers felt that the federal standards weren’t good enough, so they developed their own higher standards that some gas stations carry voluntarily. Read more here:

  • avatar

    The Daily Record has no clue how high octane fuels work. Perhaps we should send them an article about engine detonation and why high compression and forced induction engines require premium gasoline where everything else can get along fine on 87-octane.

  • avatar

    People seriously didn’t know this?

    Unless your car specifically needs premium, don’t give it premium.

  • avatar

    The D.O.H.C. neon engine ‘recommends’ premium fuel, for optimal power and efficiency.

    I have gotten up to 425 miles on a tank of premium, about 375 on regular. 25-50 miles per tank is significant whenever you’re still driving a first-generation neon=) The difference is abut 2-5mpg.

    The automobile is much better behaved on the good stuff– regular makes idle noticeably rougher, and premium gives a bit more go.

    Mother’s vulcan engine pings terribly on low grade. Terribly.

  • avatar
    Paul Niedermeyer

    This article/study is obviously stupid if it evaluated using premium in cars not designed to take advantage of it.

    But, having said that, a few years back, auto, motor & sport, Germany’s leading auto publication with very high technical standards and credibility, did a study on using rehular gas in cars that were designed to use premium. This proper study (the only one I’ve seen) showed that there were minor reductions in performance and economy (in the range of 5% to negligable). Most were in the 2% to 4% range. Depending on the car and it’s reduction in economy, it was cheaper to run regular in many cases.

    I understand the concerns, but I don’t believe that any modern engine, including force-inducted, will be damaged from running regular (the article concurred). The interplay of engine timing and octane requirement is the overiding and determining factor: reduce timing advance-no damage possible.

    Would I feed a 911 Turbo regular on a regular basis? No. But I refuse to believe that doing so will damage the engine.

  • avatar

    People seriously didn’t know this?

    Unless your car specifically needs premium, don’t give it premium.

    No, many people don’t know this. They really think that their car will make more power on premium even if it is not recommended. The believe that there is more energy in premium gas vs. regular gas.

  • avatar

    But what is the mid grade for? I have never seen a car that required it.

    Also, has anyone done the math on ethanol blends? I tried to figure it out, but I am not sure that I am right. At $2.50 a gallon, it seems that real gas would be worth 3 cents more a gallon than the 10% ethanol blend.

  • avatar

    BP claim their Ultimate fuel adds up to 28 miles per tankful

    So even though the article fails to mention what the different octane grades are for, they do admit they are responding to claims of better fuel economy from the oil companies.

    97-octane fuel

    Wow, what sort of car requires that ?

  • avatar

    The majority of modern engines have at least 1 and often more knock sensors. These engines even if they require premium, will run fine on regular,with a slight loss of power, and decreased fuel economy.

    It would be interesting to see how many people downgrade to regular, with an increase in the price of gas.

  • avatar

    I don’t know. My experience with a couple of high mileage cars was that super unleaded did indeed improve my mpg, reduced/eliminated knocking, and improved power. In my lower mileage vehicles (none of which required super0, I really didn’t see much gain and see no point in using it.

  • avatar

    Based on my rudimentary calculations, 10% blend lowers your energy content by roughly 3% and E85 is anywhere between 73-77% as efficient as gasoline.

  • avatar


    My 1998 528i recommended fuel is mid-grade. Says so on the gas cap.

  • avatar

    Im from the UK, but now live in the US.

    In the UK, regular octane is 91, mid is 95 and premium is 98.

    Since “regular” in the UK is almost as high octane as the US premium fuel, most cars, including higher performance engines will run on “UK regular” (or mid if really needed).

    Therefore, british people are looking for a reason for the 95 and 98 octane fuels…so the most obvious thought is that it might provide better fuel economy.

    I never felt any improvement in performance or mileage when I occasionally used premium in the UK…so UK premium probably is “a con”.

    US premium is definitely needed though in a number of engines.

  • avatar

    In my last car, which didn’t require premium, I could feel a very noticeable difference in power. Not 10hp, maybe only 2-3hp, but it was there, otherwise I would have kept buying regular.

  • avatar

    But what is the mid grade for? I have never seen a car that required it.

    It’s for when the car will detonate on low, but premium is too much. In my old 4runner, there must be a bunch of carbon deposits or something, so it detonates on 85 in the summer (In colorado we have 85,87,91 because at high altitude our cylinder pressures are lower than flatlanders). So in the winter when the air is cold, I can get away with 85, in the spring I bump it up to 87 when I notice the 85 detonating, and then in the summer I bump it up to 91 when I notice the 87 detonating. Then in the fall I start to bring it back down.

  • avatar

    nipplewiffle, that’s not true at all (uk low grade being as good as u.s. premium).. in the UK RON is used as the measurement. Your 98 is our 93, your 91 our 87, etc.

    I know my Protege5 would esplode if I were to put some 87 octane in it. I even have issues with the 93 octane from certain stations not being up to snuff.

    Oh, my Protege5 isn’t at all stock.. it’s turboed, making twice the wheelhorsepower the car did stock :P a stock Protege5 works excellently on 87 octane.

    Stock I couldn’t manage better than 30mpg, and now I can get 36mpg (highway.. and yes, with the turbo) because of many other mods that let the car breathe better. In that case, since my gas mileage on premium is so much better, I guess it does ‘pay for itself’.. if I didn’t drop over 10 grand to get my car to that state ha

  • avatar

    Riddle me this. Why is it that the extra octane in mid-grade gas seems to always cost ten cents and premium another ten cents. What is the actual extra production costs? Do gas stations or oil refineries make a lot more money on premium?

  • avatar

    Sorry – I knew there was some difference between the way the 2 ratings were calculated, but I didn’t think they were exactly the same – ie 87 = 91, 89 = 95 etc.. I thought the lowest US rating was still slightly lower than the european lowest rating.

    I just looked it all up, and they are the same.

  • avatar

    Maybe they should get rid of regular and mid grade, and all manufacturers should just engineer their engines to make the most of premium :-D then we’d all be getting an extra few hp for our money.

    With the costs I was used to in the UK (somewhere around $7 per gallon), buying premium all the time here in the US would still be cheap to me :)

  • avatar
    Megan Benoit

    When I lived in NE, mid-grade was 10c cheaper than regular because of the ethanol content (huge subsidies made it cheaper, where in other states, it was 10c more expensive). Ran it in my Integra, and in the husband’s focus. Never saw a gas mileage difference b/t that and the regular grade.

    Now both cars have turbos that demand the good stuff. The LGT doesn’t do too bad on mid-grade (89 or 90 octane, 91 recommended), only a slight drop in gas mileage and no performance change that we could discern. The GTI, however, gets absolute crap gas mileage on less than 91… we had to put a few gallons of 89 in it to get us to Lincoln (good luck finding better than that in rural nebraska), and it was ridiculously low. Worse was what we paid for it… being ‘premium’ gas in a rural of the country, they charged an excessive ‘premium’ price for it… we were paying probably 50c a gallon less for 93 octane here in the ATL.

    I always felt bad for people in colorado… the gas is a lower octane, and you’ll pay even more for it.

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