Today's oils, the ones rated GF-4 and SM, don't need any additives. They already have an exceptional additive package and use superior base stocks. Don't mess around with Lucas, Marvel Mystery Oil, Wynn's, or ATF. You just plain don't need it and you may adversly effect the additive balance.
That said, a little bit if ATF in the oil as a one time thing isn't going to make enough difference to worry about.
Beyond ocassionaly using chemicals (additives) for a specifiic reason, you just don't need to spend the money for snake oils.
