Originally Posted by kidd_honda
acetone will not increase your gas mileage...think about it...acetone is alcohol based and gasoline is not(synthetic fossil fuel). The acetone compound is not as dense as fuel (octane) thus acetone has a lower level of flammability. Adding acetone will give you misfire and may cause your car to stall if too much is added.
That's totally wrong actually. Acetone has a lower flash point than octane, and because it is a lighter molecule, it's flame speeds tend to be higher. While the autoignition temp is higher for acetone, this is a none issue as you are using a spark plug to light off the mixture anyway. So it is actually easier to light off acetone than octane. And since you're using ounces (as compared to gallons of gasoline) chances are it's not going to do anything anyway.
That said, I fail to see how this will help your fuel economy. Your car burns approximately 95-99% of the hydrocarbons introduced into the cylinder through running as lean as possible and EGR. So, really the best you can do is about another 5% in fuel economy using the same thermodynamic cycle (ie without totally redesigning the engine). Also, there are issues with seal compatibility and acetone, which may or may not be an issue since the amount of acetone is so small.