Viscosity?
 

More oil talk? Why are we sticking to heavier weight oil when the rest of the world including NASCAR are moving the opposite direction to 0 weight oils. I know what my oil pressure gauge likes the best, 20 50 full synthetic but with the right oil pump I am sure I could make as much pressure with a lighter oil and maybe free up some hp. It would seem to make sense that a lighter oil would last longer and free up more hp than a heavier oil.