As of the most recent refill of my truck's gas tank, I am confident that I have enough data to draw some conclusions about the effect on fuel economy of using acetone as a fuel additive.
To recap, for anyone that might have forgotten or missed out, a number of months ago, I came across the suggestion on the internet that fuel economy could be improved by using a small quantity of acetone as a fuel additive. Since I wasn't terribly concerned about the risk of breaking my truck and desperately wanted a way to save some money on gasoline, I figured I might as well give it a shot. I started out by buying a gallon of pure acetone and adding a little bit by funnel every time I filled my gas tank (before the gas to encourage mixing). Initially I saw what might have been an improvement in fuel efficiency but I was relying on my memory and quickly saw my information as purely anecdotal. Understanding how useless anecdotal information is, I decided to approach the matter in a scientific and controlled manner. Now, 22 tanks of gas and nearly four months later I am ready to draw conclusions from my data.
I have found a near linear increase in fuel efficiency up to a peak increase of about 10% at a concentration of acetone of 0.2%. Further increases beyond 0.2% result in a very steep fall-off in fuel efficiency such that a concentration of 0.25% is less fuel efficient than no acetone at all. For those that don't want to think about concentrations, 0.2% acetone is almost exactly equal to 1/3 cup acetone for every 10 gallons of fuel.
Just to be political, or something like that, for a moment, if I can finagle a 10% increase in my fuel economy out of ¢10 worth of acetone, I am doing a huge service to my bank account and the environment (acetone doesn't pollute any more than gasoline). Now let's just take a moment to think about how much of an impact there would be on the environment if every single car in America improved its fuel efficiency by 10%; acknowledging that, why isn't there a government mandate on gasoline requiring it to contain 0.2% acetone (or thereabouts)? My guess would be because your monetary savings would come straight out of the oil companies pockets, but that's beside the point. I think everyone should start adding acetone to their fuel tanks, saving themselves some money, helping the environment and cutting back on our oil consumption. Hmm, maybe I'll write my senator.
I should like to add the caveat that these results are true for my truck and other vehicles may have slightly different acetone concentration sensitivities. If you decide to follow my lead and add acetone to your vehicles fuel tank, you should perform some experiments on your own to determine your vehicles efficiency peak concentration. You should use pure acetone (solvent from a hardware store), not the scented stuff you can buy at CVS. Also, if you do something stupid and blow up your car or something, it'll be your fault alone.