I have tried acetone in both my car and my wife's car. I saw a 6-10% gain over three separate tanks in my car. In my wife's car, I had a 5% gain in one tank and no gain in a second tank.

Does this mean that it works - I can't tell you. A 10% gain in my car was about 3mpg. I don't know if it was due to the acetone or whether it was due to me psychologically changing my driving habits knowing that I'm testing something for better fuel economy.

I agree with "wait for Mythbusters" comment. A true test of the product should be done on a set course ideally with similar weather conditions and similar driving techniques. In terms of testing it for yourself, I'd do it on a car that isn't your hybrid first. I can't be certain, but after a tank with the acetone on my wife's car, an O2 sensor went bad. I've heard of this come up by several other testers, but they're not sure if it was the acetone that did it or not. It didn't throw the O2 sensor on my car.

Jeff