Adding this 4 oz. bottle of ZDD Plus to every oil change, will add an adequate amount of Zinc and Phosphorus will continue to protect your engine. ZDDPlus is an oil supplement that contains very high concentrations of the well known additive ZDDP (Zinc Dialkyl Dithiophosphate) which has been the primary extreme pressure ingredient in all quality motor oils for over 70 years. However, beginning in the late 1980's the concentration has been greatly reduced as new oil classifications have come to the market. To learn even more on ZDDP, please visit the ZDDP web site at www.zddp.com You will find a wealth of information on this product there.