I have a 2001 trans am with an ls1 engine. Currently running dino oil and want to switch to synthetic when I bring it out of storage for the winter and want to either go with royal purple or mobil 1. I have no doubt that either would never cause any problems in the engine, but if you had the choice which would you use? I can get both of them easily and they are about the same price wise unless the mobil 1 is on sale then it is cheaper. My only concern with the mobil 1 it's 10w-30 viscosity is a little lower than the royal purple and on other boards some have reported oil consumption and piston slap with the mobil 1 because it is a little thiner?