In my VY SS S2 Mobil 0w 40. Yes plenty of discusion on this site but more on bobistheoilguy who know oil and back their statements with testing, American motor so american know how. Some of their recomened oils included a Euro Castrol oil, next best Amsoil 0w 30 followed by mobil 5w 30.Because of our heat here in the WEST I went for the fourth choice Mobil one 0w 40. Now I have tried the veritable 10w 60 Castrol that the oil guy here reccomends because of the protection and shear rate and crap but honestly my engine hated it. Before people get on here and kick my head in about my oil choice I will say here and now I dont really want or care about your opinion on oil or how 1200hp speed boat engines like 10w 60 so we should use it in our stock LS1s. If you make high horsepower....... well use 10w 60 but if not look elsewere. Simple