I use Delo 15/40 diesel oil in all my older cars and trucks. The manufacturers have taken most of the extreme pressure lubricates out of it like zinc for the cat converters. Delo replaced the zinc with moly. Not as good. Thus roller rockers. I heard Rotella still has some. I use an additive from Lucas oil to replace the zinc for the flat lifters which is where most of your wear will occur. But that’s me.
