High-Zinc Motor Oil: The Protection Your Classic Car Deserves Classic car owners know that caring for their prize possessions requires very specialized care, most especially when it comes to the lubrication of the engine. Modern motor oils are great and all for newer ones, but a lot of them just lack the critical additives to adequately protect an older engine. That is where high-zinc motor oil comes in. The Importance of ZDDP Zinc dialkyldithiophosphate-commonly known as ZDDP-has been a crucial anti-wear additive in motor oils for decades. This is especially important in any engine that uses a flat-tappet camshaft, which includes most classic cars. In operation, ZDDP forms a protective layer on the metal surfaces that prevents metal-to-metal contact and ultimately cuts down on wear and tear on critical parts of the engine.