Originally Posted by Kestrel
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.
Hey guys, don't flame me on this because I don't KNOW the FACTS, just what I have learned over the last few days of reading...
Octane is a rating system, not a thing you can look at or hold. The octane rating for acetone is about 150 (from what I read). When you ad the acetone to your gas, you should use PURE acetone only, NOT fingernail polish remover. You only ad about 1-3 ounces of acetone to 10 gallons of gas (with no alcohol added preferably). You aren't looking for a higher octane rating with the acetone but are using it to break the surface tension that gas molecules have for one another. This way the gas will supposedly be a finer mist when it goes into the cylinder. The gas will burn more completely and that means more power per unit of gas which means better MPG or just enjoy the added few HP at the wheels. Also get lower emissions and a cleaner, longer lasting engine. As far as the cost goes, yes, acetone is way more expensive than gas per gallon but you aren't using gallons of the stuff. One quart should last you for 150-300 gallons of fuel. Really a cheap additive. They claim that engine parts soaked in 100% pure acetone (not mixed with gas) did cause some swelling in gaskets or seals (can't remember which), but you aren't going to be using 100% acetone but rather 7/100ths of 1% on the low end 2/10ths of 1% on the high end, depending on how much acetone gets you the best gains. That's 1 ounce to 1280 ounces of gas.