Restore optimum levels of zinc/phosphate to your motor oil with Isky ZDDP Plus. ZDDP Plus is an oil addditive 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. With the stricter emission requirements on new cars, manufacturers have removed ZDDP from motor oils. If your older car was designed to use SF or earlier motor oil, it requires ZDDP, because your engine could be damaged with the use of modern SM oils. If you have a race car that runs a flat tappet mechanic or hydraulic lifter cam, then your engine is at serious risk. ZDDP Plus can be used with regular and synthetic oils. Simply add it whenever your oil is changed.