Synthetic 5w50 Schaefer oil

Don't forget...too much zinc is a power killer. High zinc oils are ok if you're not looking for power. Zinc is a power eater. IMHO, anything over ~1600 is overkill.

The big thing is to get you oil tested often enough to see how fast you use the additive package. When it's gone, it's time to change the oil. Mileage is a variable. Some engines use more additive quicker. An example would be a SFT with rockers that are not roller in the shafts. You have a bunch of area where the zinc gets used up.

A roller crammed engine, with rollers on the rocker shaft need less zinc and use it slower.