About any oil you like will work. Its been broke in for many years and I am sure the fellow before you didn't worry much about oil. New oils have changed, thats a fact, but a stock engine with some miles on it can use what ever brand you like. 10w30 - 10w40, straight weight 30, or synthetic 10w40, any will be just fine. 20w50 will be way to heavy and diesel oils stinks ! Rotella is the worst for odor, good oil, just stinks! I run 10w30 synthetic in my '70 250 L6.
Joe
