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Adding acetone to the gasoline

  1. Jan 3, 2010 #1
    Hello everyone

    I have read and heard about proved benefits of adding a very small amount of acetone to the gasoline for our cars in order to improve the engine performance and consequently the MPG.

    Seems like the optimum percentage of this mixing is between 0.1 and 0.3% of pure acetone.

    I would like to hear something under the chemistry point of view, before checking that in my own car.

    As many mechanics state: Can this acetone addition improve the fuel's ability to vaporize completely by reducing the surface tension that inhibits vaporization of some fuel droplets, in the way of maximizing the combustion energy?

    Thanks a lot in advance.

  2. jcsd
  3. Jan 4, 2010 #2
    I have read and heard about proved benefits of adding a very small amount of acetone to the gasoline for our cars in order to improve the engine performance and consequently the MPG.
    Seems like the optimum percentage of this mixing is between 0.1 and 0.3% of pure acetone.

    Largest effect of acetone at the tiny % stated?
    Acetone will help redissolve water in the now-unavoidable ethanol/gasoline mixture, hopefully to make it a uniform solution again. Whether it will dissolve more plastic parts is a question.
    These horrible mixtures- gas/ethanol/water/acetone- need some attention to find out when they go bad. Like how much water can be handled without drowning out your car. When does this happen? Is there bad Condensation along about March???
  4. Jan 5, 2010 #3
    At those low concentrations is very unprobable you have any real effect. At greater concentrations you seriously risk to ruin your engine, because of the plastic and gums parts which goes in solution.
    Probably a little effect is in diesel fuel, not in gas: diesel fuel is less viscous than gas and has an higher boiling point, so acetone can help the injector's work and the fuel's combustion.
  5. Jan 6, 2010 #4
    I thank you for your responses. I will test the car for, say 1000 miles, to get some statistics about the fuel consumption using that 0,2%, no more.

    I will let you know the improvement, if any.


  6. Jan 6, 2010 #5
    I'll wait for the responses.:smile:
  7. Jun 30, 2010 #6
    Good evening you all

    I have driven about 3000 miles testing very small doses of acetone in my car tank.

    I started adding a slight 0.1% to the gasoline and I got a 5-6 % better MPG, and I could observe no anomaly in the engine running with the exception of a softer sound, this is an 2-cylinder-air cooled engine. In fact the car is a 1981 Citroen 2CV.

    I then increased the acetone percentage up to 0,2% and during 1500 miles the gas saving was around 10%.

    Now I am testing even higher, 0,3%. During 500 miles with a slightly better MPG, but among this, I have observed the engine temperature is higher than normal.

    As I said, this is an air-cooled engine, and its temperature fluctuates a lot depending on ambient temperature and engine revs.

    My question for you chemists; Can a 0,3% of acetone in the gasoline increase the combustion temperature?. I did not observe a significant temperature increase when adding at 0,2%.
    Can a 0,3% combustion behave very differently from that of 0,2%?

    Thanks a lot in advance for listening to me.

  8. Jun 30, 2010 #7
    This is good news if only for a Chicago deuxchevaux.
    How about old VWs? Does it increase mileage at all?
    10% is good increase,and I cannot imagine any difference in wear between 0.2% and 0.3% of acetone.
    Since gasohol costs almost 20% in mileage, can acetone bring it back/ increase it a bit?
    This is very newsworthy if true.

    My Prius will thank you. Me too.
  9. Jun 30, 2010 #8


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    I'm sorry but I just don't believe the results above. It's more likely errors crept into the measurement than that adding < 1% acetone would cause a 10% increase in gas milage (or any increase at all). It may even contradict basic thermodynamics: Acetone (and ethanol) have less energy per weight and volume than gasoline. You should get fewer MPG running on them. You may, OTOH get more power out of the engine, as it's a more combustible fuel. (which is indeed the case with ethanol, at least if running in an ethanol or bi-fuel engine)

    As anyone who watches "Mythbusters" knows, there's a staggering amount of self-delusion going on about how to improve gas mileage. And a huge snake-oil industry selling phoney fuel-additives notwithstanding, it's almost all nonsense.

    As said, adding acetone will increase the water content in your fuel. It will lower the energy content per volume. It will corrode and damage engine parts. And I'll also add that since it has a lower flash point, it can cause your engine to knock. There is a quite real possibility of doing irreparable damage to your engine this way. (and if you're under warranty, you just voided it)

    The boring truth is that modern engines run most efficiently on the fuel they were designed for.
  10. Jul 1, 2010 #9
    Hello alxm

    The role of acetone in the gasoline is not that of forming a part of the combustion elements but dissolving those tiny drops of gasoline which makes de emulssion so inefficient.

    Old carburators have problems in atomizing the gasoline well with air because of many reasons, one of them is the gasoline itself superficial tension, and acetone helps reducing that so getting a better and more uniform mixing with the intake air.

    I know almost nothing about chemistry, but after such a mileage I can tell you the above gasoline saving figures are correct.

    Thanks you all for responding and my question is still in the air; Could this acetone adding force the combustion to a higher temperature?

    Best regards.
  11. Jul 16, 2010 #10
    could you explain this a little more?
  12. Jul 17, 2010 #11
    Gasoline is a homogeneous solution of long-chain hydrocarbons, not an emulsion like milk.
    It is sprayed into cylinders as fine droplets. It remains a solution. If there is water present, acetone will help dissolve it into a homogeneous solution. When there is too much water, it will fall out (precipitate) and become a separate liquid. But the gasoline/alcohol/acetone solution ABOVE THE WATER WILL STILL BE SATURATED WITH WATER, AND HAVE POOR ENERGY CONTENT. oops soory for the caps.
  13. Jul 17, 2010 #12
    Thanks dacarls for your post. As I know nothing about chemistry I barely understand what you said.

    Is the water you mentioned that contained in the air as known as humidity ?
    Does that water help the air/gasoline be more homogeneous?
    If so, does it mean that acetone will be more noticeable when driving in a high humidity weather?.

    The real thing is that with my old car I improve the mileage by an average 12% by adding 0,25% of acetone to the gasoline.

    Sorry for using the word emulsion for gasoline when I meant gasoline/air mix.

    Best regards.
  14. Jul 27, 2010 #13
    Ok I made a try with my car, a gasoline 2000 cc Alfa 147 of year 2007. I tried with 0.25%. I noticed an improvement in the gas pedal response and a slight improvement in acceleration. I then tried with my motorcycle, an old Yamaha FZ 750 of the year 1986 with big problems of carburation, and it goes much better now. Sincerely, I couldn't believe it. I didn't make any test on mileage even because I think it's very difficult to make a comparison with all the other parametres equal (even a slight difference in athmospheric pressure is significant, for example) but I don't believe that an engine *without carburation problems* can improve mileage of 10%. If instead it had carburation problems I could believe it.

    I'm still sincerely puzzled on how such a small quantity of CH3-CO-CH3 can achieve such effect; driving the car or the bike it seems as if gas burned quicker and/or if it doesn't miss an ignition (if someone has tried driving an engine with not perfet carburation knows what I mean).
    Last edited: Jul 27, 2010
  15. Jul 27, 2010 #14


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  16. Jul 28, 2010 #15
    Alcohols are oxygenates too, but the effect is not the same. This is a perfect example of how our theoretical knowledge fails miserably against real experimentation, and I speak of myself...
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  17. Jul 28, 2010 #16


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    No practical experiment is going to show prove basic thermodynamics wrong. You have to get 10% more energy from somewhere if you're getting 10% better gas mileage.

    You did not do any real experimentation. You provided a subjective anecdote.
  18. Jul 28, 2010 #17
    Ok, but if you carefully read what I wrote, I said that I don't believe too in that 10% more energy *in an engine with no carburation problems*. Furthermore, I wrote about a quicker gas pedal response and an increase in acceleration.
    I knows thermodynamics too.
  19. Jul 28, 2010 #18
    I am not pretty sure if that 10% improvement in the MPG is a simply 10% improvement in the gasoline possible energy.

    The car has a carburated engine and we all know how much deficient is this type of system. My car's engine (602cc) maximum power is only 29 HP at 5500 RPMs. Its normal mileage is 38 MPG driving at 55 mph (about 14HP are required). This means that, at the most, the engine extracts only a 12 or 15% out of the gasoline energy to move the car, the rest is heat, mechanical looses, etc......

    Modern cars with direct injection and electronically controlled fuel injection systems have a much better efficiency. But those engines have nothing to do with my car´s one.

    What I am try to say is that a large part of lack of efficiency is due to the old carburation system, even if it is well designed and properly adjusted as I guess I maintain my carburator.

    A 10% in the MPG improvement means to increase the engine efficiency from, say, a 12% to a 13.5% and what I have experienced is that, by adding that 0.25% of pure acetone to the gasoline, my car engine eficiency (or mileage) improves by those 10 to 12 %.

    It is really far away from the modern engines performance which probably have a 100% more eficiency than my old and tiny car´s. It is a 1981 Citroen 2CV, air cooled 602cc. engine.

    The number of miles I have driven with and without adding acetone is so large that the "noisy" figures are very well "filtered" and those statistics are really reliable to insist that the actual result is a 10 to 12% improvement in the MPG when adding that small amount of pure acetone to the gas. I must say, I have not tried a larger acetone percentage, but I probably will.

    Thanks for all info you can provide me about this matter.

    best regards.
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