I'm curious, why not Type-F ATF?

Personally, I use ATF (and I think it IS type F, though I'll have to check when I get home).

I don't use any oil after a normal day's flying. But if I'm going to store an engine or if it eats dirt or water or something (I fly combat, it happens a lot), then I really fill the engine full and put it in a plastic bag because it's going to leak oil everywhere).

Your brand of fuel also matters a lot, I rusted bearings in 2 engines before changing fuel brands, and no problems since then.