East, I"ll check it out. I'm not an oil expert, just a P.E. teacher who can read an owners manuel. Heck, I don't even know what a flat tappet cam is.
I also don't know what ZDDP is. I do realize and understand that they have probably learned alot about oil and engines since 1991 and they would probably add to their manuel if they could.
Take care. I'll check into zinc and see what they say.