which oil to use

Well all the hear say aside....I know for FACT Schaeffers oil has all the zinc needed and says so right on the bottle.

I've used Schaeffer oil since I was 17yrs old, Now 30yrs old and my engines are fast, run hard, but stay cool and stay together with no cams going flat.

No issues with weather and condensation, it's compatible with stock to race, with the exception of catalytic convertors witch they have a line of oil for, for instance the 9000 series which is synthetic compatible with new cars catalytic convertors and go's a minimum of 9000 miles before change and can go 14-17000 miles.
This was tested by Darrel dotwieler who works for the company and is a good friend of mine, he uses his own cars/trucks to sample oils at various milage to then take back to their lab and begin analysis.

He runs a built 71 240z, 71 d100 318 he delivers with, and his new pos compact car, I don't like the compacts very much.lol