Okay, I'll chime in here. In my experience petroleum oil and acetone are not miscible. Water and alcohol (and gasoline) will mix with acetone, however.
So what's the lowdown on the ATF-acetone mixture? http://www.instructables.com/id/Home-made-penetrating-oil/ States pretty clearly that the mix will separate, so you have to keep shaking the bottle. Perhaps it could be made to emulsify somehow (add a surfactant?) Personally, I'd substitute paint thinner or kerosene for the acetone. I suspect it will work just as well--and it'd mix with the ATF. --Chuck
