<<This is also correct but you MUST buy the 20W-50 (Newly Formulated CLASSIC OIL FORMULA) only!!! If you want the higher ZDDP level.>> And for those of us that OWN a few CASES of SM Rated Castrol 20W50 regular oil, the reason that I have a dozen GM EOS and 2 cases of the REQUIRED Lucas stuff in route<G>!