For years ZDDP, also known as zinc dialkyldithiophosphate and often abbreviated to ZDTP, was a mainstay of many engine oil formulations. It is a sacrificial anti-wear additive that is particularly effective in flat tappet camshafts and valve train components. The big drawback was that the USA Clean Air Act pushed for a 75% decrease in emissions and forced manufacturers to reduce ZDDP levels. It is now very difficult to find an oil with a high level of Zinc.

This was a sobering blow to the lubricant industry, but new chemistries were quickly developed. The challenge was that such a significant change required costly testing to prove compliance with product specifications.

In addition to their sacrificial anti-wear properties, ZDDPs are effective in creating thicker lubricant films by chemically bonding with the surfaces they coat, forming tribofilms that protect metal-to-metal contact. They can also function as effective antioxidants, decomposing the hydroperoxides formed when base oils oxidize in the presence of heat and pressure.

Adding a zddp additive to synthetic oil is not an easy task, and the first thing that any petroleum engineer will tell you is that pouring in foreign chemistry is never a good idea. ZDDP is acidic and mixes poorly with detergents and other additives in the oil. This causes chemical reactions that can actually reduce the effectiveness of the sacrificial anti-wear protection. A better solution is to use a premium oil that already contains the proper dosage of ZDDP and phosphorus.