What gives everyone the idea modern engines are so oil grade sensitive?
General design specs call for them to work from -40 to +122F. At startup temps the difference is beyond huge. While they are liquid cooled you will see a significant difference in operating temps between 5000 lb at -40 on flat ground and 19500 lb at +122F on a 7% Grade regardless. While I can certainly see the argument for 0W-20 at one extreme.and 15W-40 at the other I think the reality is that it is relatively a minor difference when you look at the operating viscosity an engine is designed to deal with.
General design specs call for them to work from -40 to +122F. At startup temps the difference is beyond huge. While they are liquid cooled you will see a significant difference in operating temps between 5000 lb at -40 on flat ground and 19500 lb at +122F on a 7% Grade regardless. While I can certainly see the argument for 0W-20 at one extreme.and 15W-40 at the other I think the reality is that it is relatively a minor difference when you look at the operating viscosity an engine is designed to deal with.