ive always ran full synthetic, but keep this in mind... once you put synthetic in your car, you can NEVER go back to regular oil.
How is that? I have done it and didnt have a promblem
99 Grand Prix old build- CAI, Custom exhaust, HV3, Stage 2 TB, custom tune, ported heads intense s1x cam, headers.
Nothing great Just a small T66 Turbo with a Hv3 On a stock tranny untill i finish the other one.