Re: Zinc additive??
If I had a high dollar flat tappet cam engine, I'd step up to the plate and add ZDDPlus to the oil. 4 0z bottle is $10 and treats 4-5 quarts of oil. For some piece of mind, I've been addding STP Oil Treatment with ZDDP with each oil change to my '68's L48. STP declares, "if you use one 15 oz bottle to 4-5 qts of oil, it will provide the same protection as the older motor oils provided. The amount of ZDDP in STP is proprietary." So far so good. Fingers crossed. Knock on wood.
Both optimists and pessimists contribute to society. The optimist invents the automobile, the pessimist seat belts, head rests, disc brakes, and air bags.