Some motor oils use the additive ZDDP include Amsoil Z-ROD, Amsoil Premium Synthetic Protection, Amsoil Break-in oil and Amsoil Dominator. ZDDP is considered by many automotive enthusiasts to be a useful in preventing engine wear. However, since its introduction in the earlier years of the automotive industry, its use has decreased due to regulations setup by American Petroleum Institute.
Amsoil Z-ROD is an oil that contains some traces of ZDDP. It is used primarily on older hot rod engines that use flat-tappet camshafts. It also helps prevent against corrosion and surface rust.
Amsoil Premium synthetic is used for normal vehicles, while Break-in oil is used specifically for high-performance and racing engines. Break-in oil contains some of the highest levels of ZDDP, which is combined with the other additives for a friction free formula. The result is a stable and smooth lubricant, that allows an engine's piston rings to easily set in place.
Amsoil Dominator contains the most ZDDP in its formula. This oil is also used specifically for racing applications.
Prior to the change in 2004, ZDDP was debated in the engine building community as something that was without equal in terms of protecting against engine wear, notes Amsoil. This idea eventually lead to believing more ZDDP would be beneficial to the engine. Although it was better for the engine, it disallowed the catalytic converter to properly function, which released more harmful toxins into the air.