I've been thinking about the tendency of oil to shear in some applications. I was trying to figure out why a manufacturer would spec a 5W-30 over a 5W-20 if they both came out of the crankcase at 8.6 cSt.
Do manufacturers assume a one grade loss in use?
IE 5W-30 will be a 20 Grade and 5W-20 will be a 16 Grade?
Do manufacturers assume a one grade loss in use?
IE 5W-30 will be a 20 Grade and 5W-20 will be a 16 Grade?