I had a tech tell me once to add some ATF to the engine oil to help free up a stuck lifter. I don't recall if it helped. I also recall the detergent levels of ATF being higher to prevent valve bodies from gumming up. I suppose it would keep the engine clean but I don't know how it is for a combustion chamber lubricant. Gasloline will keep engine parts clean too but it don't do much for reducing friction