By on August 29, 2011


Robin writes:


Longtime reader, first time writer. I love reading your stuff, well worthwhile.

My query is about fuel additives, after-market specifically. I have used the Lucas Oil products and found them to produce a mile or two better MPG in my 94 D21 four banger. (Note: that’s a Nissan Hardbody – SM)

What is your take on additives? Have you found any others to be of significant value to the user/user’s vehicle?

Sajeev answers:

Great question, with a pretty short answer: additives are usually useless in cars that are well maintained. That’s in general. Some people swear by Lucas additives, but I am not sure of their benefit over consistent usage of synthetic fluids over the course of a vehicle’s life. And that’s worth keeping in mind, no matter how “special” you feel your circumstances may be. Can the magic bottles really be that special in something as honest and durable as a 1990s Nissan truck? Your case seems pretty clear cut.

Then again, fuel system additives are one exception, they sometimes do a great job at removing gunk (especially with varnish/corrosion/deposits that supposedly occur with E10 gas) in the fuel system, the tiny screens in the fuel injectors in particular. I haven’t personally experienced a benefit from fuel injector cleaner, but I do occasionally use it as preventative maintenance on my old cars in the land of E10 at the gas pumps. But a mile or two better MPGs?  That’s pretty impressive.

That said, make sure to change your fuel filter as per manufacturer recommendations. Or sooner. That’s often a bigger problem for your fuel system.

Bonus! A Piston Slap Nugget of Wisdom:

My only additive of recommendation is Seafoam. Seafoam seems to fix everything…in motors with a lot of miles and a lot of carbon buildup. Sure, it makes a colossal mess while de-carboning the upper half of a motor, but it often improves throttle response, fuel economy and sometimes even emissions. After it increases your carbon footprint exponentially, ‘natch. This stuff is also supposedly a good fuel system cleaner, oil gunk remover and probably helps men with their Viagra-related concerns. (kidding!)

Not that I recommend everyone spend the $8 or so to try it out on your motor, but if you start running out of options after a proper tune-up on your old hooptie fails to give you satisfaction…give it a shot.

Send your queries to [email protected] Spare no details and ask for a speedy resolution if you’re in a hurry.

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42 Comments on “Piston Slap: Fuelish Thought on Additives?...”

  • avatar

    On my vehicles (2003 Subaru Forester XS & 2005 Lexus ES 330) I use nothing but Amsoil synthetics. Once a year on a long highway trip I put a bottle of Amsoil P.I. complete fuel system cleaner. Keeps things clean & I personally get an overall MPG increase of roughly 3.8% so it does work. More info here…

  • avatar
    Cammy Corrigan

    Fifth Gear talked about this topic before.

    • 0 avatar

      If your engine is not designed for higher octane fuels, using higher octane fuels is counterproductive, and can actually INCREASE intake deposits. Higher octane fuels by their nature are more difficult to burn (this reduces their propensity for preignition in a high compression engine). In a lower compression engine, they are less likely to fully combust, leading to carbon deposits in the combustion chamber and intake manifold. In the US all fuels are required to have detergent additives to keep the fuel system clean. Use of higher octane fuels In a vehicle not designed for them is a waste of money and can actually cause engine spark knock due to carbon build up. At this point you would then need to run a product such as sea foam or the like to remove deposits you never would have had in the first place if you simply opened your owner’s manual and read about your fuel requirements.
      In the video, I would venture to guess that the reduced power output is caused by the additives increasing fuel octane, thus making the fuel more difficult to combust in the engine. The resulting incomplete combustion of the fuel and air charge is why the power output is decreased. The octane rating needed by a given engine is the lowest one where the engine does not suffer from preignition. Anything more is unnecessary and can result in carbon deposits.

  • avatar

    Are fuel line magnets and air inlet turbulators considered additives?

    This topic should be reserved for April 1 . . .

  • avatar

    I have used the Lucas Oil products and found them to produce a mile or two better MPG in my 94 D21 four banger.

    I find this hard to believe, frankly. Unless the additive has significantly more energy content than the gasoline that it replaces, I can’t see how that is possible.

    I do run the occasional bit of Techron through my car in the hopes that it provides some added detergent value, but I may be wasting my money. (Is there any proof that running additional detergents beyond what are already contained in Top Tier gas helps to make things better? I honestly don’t know.) Just keeping the tires properly inflated and keeping the fuel filter maintained would probably provide more benefit.

    • 0 avatar

      Maybe it’s Psychosomatic; you think the engine is running more smoothly so you lead-foot less and get better mileage.

      • 0 avatar

        That’s my take on the subject.

        I’d love to conduct a placebo experiment. Have some attractive ladies hand out free samples of some miraculous new super fuel additive to people who have just filled up at a gas station. The samples are completely free-of-charge, but we’d love to hear feedback from you as to how much your mileage has improved, how much more power you feel, how much smoother it now runs etc.

        The impressive looking bottles with lots of fancy technical terms on the label would contain…

        …exactly the same fuel they had just filled up with.

    • 0 avatar

      I assume the volume of the addittive is roughly 200-400 ml, which if it has about same energy content as gasoline, will take you a few extra miles in a compact car.

  • avatar

    Sajeev, is there any case where it’s NOT a good idea to seafoam an engine? My ’88 Country Squire 150k is burning a little oil, on it’s last legs, really. The oil pump is failing, I’m running 20w-50 racing oil in it just to prolong it’s life, per my mechanic’s reccomendation. The exhaust is falling off but wired up (I’m not ever replacing it).

    The next stop is the junk yard when something major goes kaput. Does Seafoam have the potential to kill a car or make it consume more oil after it’s been treated?

    Oh, and before anyone gets on my case for driving this “horrible” dinosaur, I love it, & my work commute is 2 miles each way. I can get a month or more out of a tank of gas even with driving to town, how many of you econo car drivers can say that? (Besides Volt/Prius owners) Oh, and there’s no emissions testing where I live. Plus I got 23 mpg on the highway with it recently, just as good as a newer Toyota Tacoma (real world #’s).

    • 0 avatar

      I wouldn’t bother. Save the money for a take out motor from the junkyard…or leave it at the yard.

    • 0 avatar

      If you’ve got a bad oil pump do not put any seafoam in the engine it’s a good way to end it’s life. Chances are it’s not the oil pump but a plugged up pickup screen. The crap that it will break free will end up clogging what ever little passages there are currently through the screen. It can also cause and engine that is burning oil to start burning and/or start leaking it at an even faster rate when the gunk that was holding it together is knocked loose to plug up the pickup.

      • 0 avatar

        Thanks Scoutdude & Sajeev.

        Educator(of teachers)Dan, I’ve got my eye on a number of replacement vehicles on CL within a certain distance of where I live. One of which is a 1991 Mercury Colony Park with 116k, limo tint on the back, leather interior, just needs valve cover gasket and battery. $1200 obo. I can get $500 out of my Squire at the junkyard or strip the usable parts off it & save them for the new one. My current car has rust holes in the lower door. It’s more beater-class than restoration class.

        There are also a 1965 Austin Princess, 1972 & ’73 Dodge Dart (all 3 $800 ea), & a BROWN 1980 Plymouth Volare Wagon with aftermarket A/C (for $700). Plus plenty more crazy options like a ’63 Chevy Nova with a 6 cyl, powerglide, 63k, radio delete, carpet delete, for just $1100. Or how about a ’63 Renault Dauphine? I kind of have a wandering eye right now.

      • 0 avatar
        Educator(of teachers)Dan

        That is an eclectic list my friend. Good luck.

      • 0 avatar
        Steven Lang

        SexC stick to the later model cars. The Country Squire you mentioned would put all the others to shame in real world commuting.

        Plus they are wondrous haulers of ‘stuff’. God I love those cars.

      • 0 avatar

        Snag that Colony Park quick offer them $1k. Snag the battery out of the Squire and any other parts that could be useful like swapping your tires if they are better. Jump start the Squire and drive it to the junkyard and collect your 2 tons worth of scrap value. You could easily spend $500 on fixing the oil pressure issues and you’d still have a car that was rusty and burns oil. Alternately you could just keep the Squire until it dies but then you’ll need to figure out a way to get it to the wrecking yard or have them pick it up and give you a lot less cash.

  • avatar
    Almost Jake

    I can only vouch for seafoam. I slowly add it to the intake through a vacuum line, let the engine sit for 30 minutes, and then piss-off the neighbors with plums of smoke. My cars seem to run smoother after treatments.

    As for Lucus Oil, I used the upper cylinder lube on my 2001 Accord and found it seemed to smooth out the engine. Though, I didn’t notice any MPG improvements.

  • avatar

    Perhaps I’m just a sucker for a placebo effect, but i’ve found the right additive for the right motor makes a difference.

    Seafoam is a favorite for all small engines and marine motors.
    BG’s 44k made both high mileage Q45 motors run smoother, I’d just add a bottle to a full tank before each oil change.
    Intake foggers for cleaning the Q’s intake tracks made a huge difference in the idle quality on both cars and a bottle of Iso-Heat each month during to winter seemed to help too.

  • avatar

    Every owner’s manual I’ve looked at recommends against fuel and oil additives. However selling snake oil has always been quite profitable, even dealers’ parts departments get in on the action.

    • 0 avatar

      My dealer sent me a “coupon” for a Techron fuel system cleaning for just $260. Such a deal. If I bring in my own, maybe they’ll only charge me the $250 for labor. That can must be a real pain in the ass to open to rack up that much in labor costs.

  • avatar

    I throw a bottle of Chevron’s Techron cleaner in every oil change. I’ve never had injector issues in any of my cars (probably 300K miles between vehicles). I recall a buddy have fuel gauge issues once and I told him to try a couple bottles of Techron first and it cured his issue.

  • avatar

    Regarding oil additives, I can give you my perspective from the commercial truck industry since I think it applies to passenger vehicles as well.

    The trucking industry is obsessed with increasing fuel economy and long engine life (a reman diesel is over $25k) and oil additives, particularly Lucas, are promoted constantly. Before deciding to spend an additional $30 per oil change on Lucas products I talked to manufacturers reps from both Cummins and Detroit Diesel.

    Both reps were adamant in not using oil additives for the following reason: manufacturers of the major oil brands have spent millions of dollars developing base stock and additive blends to optimize the performance of their respective oils. Adding additional chemicals in the form of oil aftermarket oil additives screws up the OEM chemistry of the oil, and may actually make the oil WORSE as a result. If there was some magic chemicals that would make motor oil more effective, motor oil manufacturers would have every reason to put it into their oil blend and market the hell out of it.

    I took this advice and have 4 engines with over 1 million miles of hard service without any rebuilding. Knock on wood, and thank you Shell Rotella.

    In addition, none of the major transportation companies (that I know of) use these additives, and they have every incentive to do so. Interesting that all additives seem to be marketed to the do-it-yourself market (which is not necessarily sophisticated regarding oil chemistry), not engine makers, vehicle fleet managers, or vehicle OEMs. Again, if there was some magic oil additive that would increase fuel economy vehicle manufacturers would be all over it just to help achieve CAFE requirements.

    However, I have had good luck with fuel injector cleaners in big trucks, but never noticed a difference with my personal vehicles. YMMV.

    • 0 avatar

      Snake oils. At best they only lighten your wallet, and as Toad points out they can have a detrimental affect on the complex chemistry of the system they are added to. This is especially true for engine oil and even more so for automatic transmission fluid.. Honestly, if a manufacturer could realize an increase in fuel mileage of 1 to 2 MPG simply with the use of these magic additives (especially in this era of CAFE requirements) your engine compartment would be fitted with reservoirs for the injection fo this crap as you drive. I can’t state this any simpler: FOLLOW THE MAINTENANCE SCHEDULE PROVIDED WITH YOUR VEHICLE. Ignore any menu services that a dealer may recommend with the idea that it will better protect your vehicle due to the “unique driving stress” of your particular geographic location (severe New England weather was always the hard sell in the dealerships I worked for). Now where is my tinfoil shield, the gasoline companies are probably messing with my engine’s PCM by satellite and ruining my fuel mileage.

  • avatar

    Is there any truth to the notion that ringing your engine out periodically can help remove carbon build up? I’ve heard this in a number of places, but can’t be sure.

    My only experience with really ringing my engine out has been on freeway onramps when not stuck behind somebody who decides that 50mph is a perfectly legitimate entrance speed onto a 70mph freeway. I even bounced it off the rev-limiter last week when I got a little too enthusiastic (that was the strangest feeling I’ve ever experienced).

    • 0 avatar

      I believe this is primarily with turbo motors and to some extent it is true. If you idle around and don’t really get into the turbo it cant build up some deposits, flooring it will often cause a puff of black smoke as they soot gets burned off the turbo

    • 0 avatar
      Educator(of teachers)Dan

      Totally depends on the engine. Northstar that belongs to your grandmother and never sees anything higher than 3000 RPM, heck yes. Other engines I have no idea. A nieghbor of mine used to take his mother’s mid 80s Grand Marquis out on the highway and give it the old “Italian Tuneup” about twice a year because the old girl never got over 35mph dinking around the little burg of Continental, OH. Did it do any good? Who knows.

    • 0 avatar

      I bounced off the rev limiter years ago in my Saturn, when I was taking it in to get a new engine (mostly under warranty) because the old one had the oil use problem. I just wanted to see what would happen, and yes ,it was a very strange feeling.

    • 0 avatar

      For the pre-computer-controlled cars, it was very advantageous to do the “italian tuneup” or whatever you like to call it, especially on cars that seldom saw freeway use. I used to maintain a number of 1960s-70s American cars for elderly widows in my mom’s prayer group. I would always fully warm them up and go out on the bypass highway and kick them down into 2nd gear at about 40-50mph, keeping my foot to the floor for several seconds at a time. The plume of carbon out the back was always highly entertaining (not to mention watching the people behind me back way off)!

      For the newer cars, I’m not so sure that doing this is beneficial, BUT on turbocharged diesel cars that have variable-vane turbos (not sure if this applies to gas-powered engines with turbos or not) it is very important to fully exercise these or they will soot up and stick in place.

  • avatar

    Keep in mind that additives very much work for diesel engines. Most prominently cetane boosters due to the effect cetane levels have on gas mileage and the inconsistency of supply in the united states.

    I did some tests since my commute is very consistent and I have been tracking mileage for some time

    I did one tank where I dropped my speed to below 70mph (usually do 80) and gained 2mpg

    I did another tank where I drove my normal 80 but used Opti-Lube XPD fuel additive and gained 2 mpg

    When I remember to use it I consistently see a 2mpg improvement from the Opti-Lube XPD

    It cost me about 50 bucks for enough to treat 500 gallons so 10 cents a gallon. my average price per gallon of diesel is 4.20 in 25,000 miles of logging. My average mpg being 44 that means my cost per mile is 9.5cents, using the additive my cost per mile is 10.6 cents per mile so its NOT a cost savings. It does however have other benefits as far as fuel system maintenance and wear

  • avatar

    How could you trust anything branded Lucas anyway? Or as long as it’s not electrical stuff it’s fine?

  • avatar

    I ran a couple of bottles of Techron through the Fit recently. It had been stumbling a bit and fuel economy was down several MPG from last summer. I did see an improvement, and overall the engine is smoother, but it wasn’t a cure. That would have been the valve job. Back to normal now.

    In the Alfa, I just go for an Italian tuneup every weekend. It’s the most satisfying form of auto maintenance I can think of.

  • avatar

    What I’ve heard most successful/used:
    *Zee Italian Tune-Up
    *New/wire-brushing/re-gapping plugs
    *Replacing old, crappy plugwires, dizcap, rotor

    *Lubro-Moly MOS2
    *20w50 or Rotella-T + 25% ATF (was for a high-mileage VW 4cyl, note: this initially dislodged much more than prepared for)
    *50%oil 50%Kerosene or Diesel for a short-idle-then-flush. (otherwise crudely referred to by our enlisted motor-pool guys as “The Diesel Douche”)

    Also: BobIsTheOilGuy:

  • avatar

    Just used Seafoam on my 4-stroke weedeater Saturday. Motor was hard to start, idled rough, and wouldn’t rev at all. Dribbled Seafoam in and 5 minutes later was running full throttle like brand new. Also used it on a 60 year old 2-stroke outboard. Runs like a champ. Best stuff ever!!!

  • avatar

    Even with my mostly ancient fleet, I stick to dino-oil and few additives. Once I notice that any of them are having any loss of compression, I will generally start adding Restore to the oil. That seems to even out the compression issues.

    I know that on certain cars (and diesel truck motors, the big ones) the element Zinc is a necessity for smooth operation, usually specified the oils that have ZDDP listed on the label. Oils like Rotella T have the ZDDP and with the right viscosity can be used in car motors.

    A co worker of mine has used something called Motorkote to effectively kill a the noise from a bad lifter, I noticed on the side of the bottle that it too had ZDDP. And other stuff. I will wait to see if he develops other issues.

    I occasionally add Techron to the fuel tank to ‘clean’ the injectors, but I buy my fuel at several ‘bargain’ gas stations, at least for the cockroaches. It seems to smooth out the idle for a while. I haven’t used a ‘dry gas’ or ‘Heet’ type of additive to the fuel since carburetors went away. In this part of the midwest we get ethanol in our fuel in the winter, so that hasn’t been an issue.

    I do buy/specify good oil/air/fuel filters. OEM at a minimum. I’ve had K&N’s on a couple of cars, but I never saw a fuel mileage increase from that alone. For as little as I drive in a year, (>10K miles), the K&N’s would eventually dry rot. I went back to paper filters.

    I use as few as possible extra chemicals in the motors. Can’t say that I’ve seen many negative effects from it.

  • avatar

    snake oil – for the cost of the additive you could purchase a gallon of gasoline.

  • avatar

    FWIW, this is my routine when buying a new car and it has worked very well for me for decades:

    At 1000 miles after break-in, I personally change the oil and filter and add fresh oil of the grade recommended (I prefer Castrol dinosaur-oil) and a quart of PTFE (any brand since PTFE is Dupont’s PTFE by any other name).

    At 4000 miles I change the oil and filter again and add Castrol Synthetic of the recommended grade and a PTFE Fram filter. At the next tankful of gas I add 1 ounce of Marvel Mystery oil, and do so about every three tankfuls, or so.

    I do keep a tiny notebook in the glove compartment to make notes or comments. Great show and tell when you sell your car, too.

    Techron works extremely well on old cars and high mileage engines that burn oil. I pulled the heads on a Ford 5.8 that had been using Techron and run on Chevron Supreme and those valve seats were downright shiny. No carbon, no crud, just clean valves and stems.

    The thing to keep in mind with gas/diesel additives is that a little goes a long way. Too much is counterproductive.

    For carbureted engines I highly recommend GumOut spray cleaner in a can with the engine running at about 4000rpm. It worked for me when I was in Europe running my American cars on that cheap Esso gas not fit for Fiats, 2CVs and Ladas.

    The quality of gas that one puts in their gas tank probably has more to do with how well your fuel system functions than anything else.

    I recommend Shell Premium in my area as well as Chevron Supreme – in my area they’re the same gas that comes from the same tank farm. All others smack of sulphur, and you can smell it. Stay away from sulphur gas, it builds up on your valve stems and seats.

    If your engine burns oil you will also see a lot of build up over time of crud on the valve stems and seats as the oil additives are left behind. Marvel Mystery oil will dissolve the crud over time. My experience anyway.

  • avatar
    MRF 95 T-Bird

    I use Lucas additives fuel and oil in my 95 T-Bird 4.6. The oil additive seems to keep the valve seals in shape and lessen oil consumption. I used Restore occasionally in my 87 3.8 T-Bird and it ran well till head gasket failure at 187k.

  • avatar

    I use Penrite upper cylinder lubricant (same stuff as Flashlube) to protect my LPG converted Lancer from exhaust valve seat recession (VSR). The car’s manual specifically states my engine is not suitable for LPG. It doesn’t have hardened valve seats and the bearings may not be of the right composition. Therefore I inject fluid to protect the valve seats through the intake manifold.

    After 30k km on LPG the seats were examined and found to be within expected wear for a 90k km engine. An LPG specific oil (also Penrite) is used to resist oil nitration and possible damage to bearings from oil acidification.

    The installer LPG mechanic stated VSR doesn’t occur on modern engines designed to run on unleaded fuel, but many posts from VSR suffering LPG converted car owners on the Internet disagree. Easier to burn $10 of fluid per 10k km than risk an expensive engine rebuild.

  • avatar

    Nobody uses that Z stuff Carrol Shelby pimps?

  • avatar
    Ian Anderson

    Only additives we use in my house are Seafoam, Lucas for the oil and Stabil for the winter (and in the generator etc). The Seafoam’s good for pissing off the neighbors, especially if said neighbors piss you off with car-related stuff. That and it does seem to work, made the S10’s 4.3 idle smooth (well, as smooth as a 90º non-balancer V6 can be) and under the valve covers looked better. My Dakota’s 3.9 is next!

    The Lucas we use in the Metro since it has leaky valve seals and puffs oil smoke at start up. It seems to have cut down on that a lot, either me or my dad will add 1/2 a quart to the oil every change. Before I started driving it the S10 got some benefit from it too- the 4.3 suffers all the same high mileage valve-seal problems as its small block parents. Now I just ignore it and check the oil!

    As for the Stabil it’s good for keeping gas from turning into varnish, or at least our generator, lawn mowers, weed whacker, hedge trimmers, etc make it seem that way.

  • avatar

    been out of town and return to find this piece on my favorite site!

    My cousin had some thoughtful input that made me feel a bit better about using Lucas: ” I use Lucas in all my cars. Not for fuel economy but to keep rubber parts lubricated (especially on the 30 year old bimmer). Ethanol is horrible for that stuff. It also helps to lubricate the fuel pump and its associated parts and the upper cylinder walls as well as helping to prevent carbon buildup.”

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