ZddPlus is an oil supplement that contains very high concentrations of the well-known additive ZDDP (Zinc Dialkyl Dithiophosphate), which has been the primary EP (extreme pressure) ingredient in all quality motor oils for over 70 years. However, beginning in the late 1980s, the concentration has been greatly reduced as newer oil classifications have come on the market.
The EPA has put stricter emission requirements on new cars that influenced manufacturers to remove ZDDP from motor oils. If you have an older car that was specified to use SF (1988) or earlier motor oil, its design requires ZDDP. Your older performance car could be damaged with the use of modern SM oils prevalent today. Cars equipped with flat tappet cams need ZDDP because of the high-pressure points. Newer cars have roller rockers and ZDDP is not needed in those applications