Use Redline, Brad Penn or Joe Gibbs hot rod oil. I think Royal Purple also has a high zinc hot rod oil made for older engines. Be ready to pay the $6 a quart for it. The zinc additives will work but I have a problem with messing with factory oil recipe. They spend millions of dollars developing oil and then we come along and add something that the engineer didn't figure into the formula. Might be no issue but I have learned he hard way a few times and would rather buy an oil made for the application right from the start