Originally Posted by xfire2005
Exceeding industry standards and the major leading builder requirements is the cornerstone of the performance reserve that lets Mobil 1 0W-40 keep performing well after conventional oils cannot. Mobil 1 0W-40 provides the widest range of protection -- providing the
extreme cold start protection of an 0W grade and the high temperature protection of an SAE 40 grade.
So is it ok to use 5w-40 if there are no 0w-40 available? My limited understanding of oil viscosity is that it has more to do with expected temperature variation rather than the actual "quality" of the oil. Maybe in the colder regions specially in the winter 0w-40 would offer better protection at starup because it would flow more freely but once the engine has warmed up then it would not matter. So my line of thinking is that in the temperate regions like California or Florida 5w-40 should be ok. Would I be doing harm to my engine if I did this?