I have a 56 GMC with a 316 or 317 pontiac engine. When the truck was in Use( last plates and last use are 1975 plates) we used mobiloil special. I think in the 50's and 70's mobiloil contain ed zinc. My question the truck has just been started up again after all those yrs. and what kind of oil should I use?
GM does have an additive in about a 4 0z container that may contain Zinc. Shell rotella has been suggested. All adviced appreciated..tom
