Hi been perusing all over here and have gathered much need info regarding 5w-20 oils, Syn, dino, filters, UOA and just plain over jealous car love! Anyway, My vote is for Arco(?) graphite oil back in the late 70's very early 80's. It would foam like crazy and I'd get engine noise after cruising 65 for about ten minures(speed limit was 55 back then here). The oil spent all of 30 miles in my crankcase. And it wasn't over filled Any other Bad ones from the past?