More thoughts...

I believe that adding 2 oz of acetone to 10 gals of gasoline will increase it's octane rating and therefore allow it to vaporize & burn more efficiently.

But, I do not see how it can increase mileage in today's engines. If it did, it would indicate that we are not getting a complete burn of our gasoline during combustion... and we would have gasoline vapors coming out our tail pipes - in addition to the CO, H2O, NO, ...

I know this may have happened 40 years ago (I've seen video of hopped-up cars with spark plugs in their tailpipes that would ignite the un-burnt gasoline vapors), but would this still happen in a modern FI/ECM car, using good, clean-burning gasoline? I know the cat does do some minor post-combustion "burning" of the exhaust gases, but with today's engines - I can't believe they are burning 20% of the un-burned fuel??

Lastly, if this were true, would the EPA, Honda, Toyota,... also have to be in bed with the oil companies? Wouldn't it instead be to their advantage to recommend this to their car buyers so that we'd have low emission Civics/Scions that get 75 MPG by just adding 2 oz's of acetone? This doesn't seem like a secret that the oil industry could keep under their hats - if it truly worked...??