Acetone is a reactive material, I have tested it for several years on a Buick Lesabre.
It seemed to have an affect in the winter time on fuel economy and inversely during the summer time.
The affect did not increase fuel economy enough to exceed the cost of the acetone. Likewise concentration had a role but not much of a role.
One affect I noticed every time I added acetone was that my scanguage would be screwed up massively!
But the actual fuel economy over many identical trips was affected minimally.
I have a feeling it "doped" sensors which probably makes it seem like (for people who followed the other guys use acetone crap site with a scangage) that fuel economy immediately jumped on the scangage but again if you check your actual fuel economy useing your gas receipt and math its affect was minimal.
It is however in most injector cleaners, some of the octane boosters (in a bottle) and even in the legendary seafoam if memory serves, great for cleaning but not much else, unless it somehow gets cheaper than gasoline.
In the lab acetone, like ethanol has non-linear, non-ideal vapor pressure affects when mixed with gasoline. This means that it could have more of an affect on octane and flame front than expected. That being said it is too expensive to find out the sweet spot for its use like one would do with 30% e85. Maybe a racer would like it to dope his gas to 100 octane but I really can't see any practical use for the stuff, not to mention it vaporizes easily and would quickly end up in your tank vapor system.
http://www.turbofast.com.au/racefuel13.html
Cheers
Ryan