I run AMSOIL: sae-60, 20w-50, even 10w-40. . .i takes a darn cold winter before go to 10w-40. . .
My ford has 15w-50 Mobile one in it right now we hit the 20's at night starts just fine. . .
My GMC runs straight 60 year round start's all winter with just a tap of the key. . .
Mike !