If you left your car warm up. Then I'm sure it can't be that different. The viscosity is already factored into the 5w-30 rating. Its just the Amsoil, rotella T, or VR-1 has zinc and what not in it that is said to help out some on bearings and rods.how hard is it on your car to run a thicker oil like that? I work at a oil change shop and i was going to throw probably a penz platinum 5-30. Would it be better to go with a 5-30 and more of a racing oil like amzoil? or the rotella?...