OGTS, the acetone "myth" was "debunked" by MythBusters, who didn't do a good job and are often subjective at best. Science has proven in several tests (links above), that 2-3 ounces per tank can greatly increase gas mileage because you burn more actual fuel. Straight gasoline or E-blends tend to waste some and not actually get burned up. MythBusters and Snopes used more than the scientifically recommended amount, which has been tested and proven to reduce gas mileage if you put too much of the stuff in. Considering I've seen and know of people who have received much greater gas mileage due to that and not plowing 85mph on the highway, their gas mileage has almost doubled.

Why would refineries want to sell half as less gas by mixing it in? Secondly it has been proved to eat rubber gaskets over a period of several years if you use it regularly. Most cars weren't designed with tougher gaskets that CAN handle acetone, thus another reason why the refineries don't mix it in. To avoid lawsuits and to sell more gas.

I'd say it's just as much effective as it is bunk.