A friend of mine ran into an old guy who worked at/for/ or in conjunction with Marvel Mystery Oil. The old guy told him it was Automatic Transmission Fluid.
I like it for the reasons others posted: It smells good and makes me feel good. I use it in my 47 Indian (flathead). My opinion is that the best thing you can do for your fuel is to stay away from ethanol blends if possible. At least around here (east Tennessee) it is becoming an option (for a higher price) at more and more gas stations.
joe
