whomp whomp whomp
I ran 15w40 when my ramcharger's 318 was worn right out. when cold I got 20-25, when warm I would get 6, sitting in traffic it dipped to 0, couple weeks later I changed the motor with my dad.
IMO anything higher then a 10w30 is for either a racecar, diesel, or piece of heavy equipment. If your motor has standard clearances it should be 5w30-10w30.
I believe the factory specs for my ramcharger(84 ramcharger with a 318 2bbl) was 6 psi at idle, and I think it was 20 psi at 2K.