CurlyDave
Elite Member
2x
For some reason that trips up some.
Actually, the 5W-40 provides superior protection both in low temperatures and high.
It has to do with the way multi-grade oils are made and something called the "Weissenberg Effect". The analysis is complicated, but multi-grade oils generate a force which tends to keep crankshaft and piston rod bearings centered under use. Single weight oils do not do this. The larger the difference in the two weights rated, the larger is this effect.