I think: keep good oil in the engine/trans, change often - all good. Some time back a friend recommended ENGINE RESTORE, seems to work great!!! Anyone tried it? The other product I love (haven't tried in engine) is the LUCAS OIL STABILIZER. Used in Trannies and rear ends...what a difference, smooth, nice! I know there are tons of additives (I use Marvel Mystery Oil in the gas & Diesel), I see Slick 50 makes some as do other companies. Anyone got any feedback on this?