Originally Posted by paoester
More facts because this thread seems to need some more instead of speculation:
M1 AFE 0w20 is 140x too thick at -5 F, while M1 5w30 is 230x too thick (hot running viscosity 10 cSt as the basis).
Which do you want to start your engine with at -5 F in N. Wisconsin?
Both would be pumpable and neither one is detrimental to the engine.
The question should be about the MOFT at operating temperature, not about starting at -5F.