ZDDP is a heat-activated chemistry that forms a "tribofilm" on metal surfaces to protect them from wear. When the moving parts in your engine create friction and heat, this chemistry decomposes and forms a thin layer of protection on critical metal surfaces, such as cams, lifters, and valve train components.

In addition to its wear-protection capabilities, zddp oil is also great for corrosion inhibition. This is because it bonds to the metal and prevents it from rusting away as it moves through your engine.

Zinc dialkyldithiophosphate, or ZDDP, is the most commonly used zinc-based antiwear additive in motor oils. It is found in both mineral and synthetic engine oils, although the latter tends to have higher concentrations of this antiwear chemistry.

It is a polar molecule that is naturally attracted to steel surfaces, which helps it form a sacrificial film that protects these surfaces from damage. Other additives like detergents and dispersants compete with it for surface space, which can negatively affect its ability to do its job of lubricating.

When used in combination with phosphorus, ZDDP provides the most effective antiwear performance. However, phosphorus is also responsible for some catalyst poisoning problems, so automakers are increasingly focused on improving other performance parameters rather than adding it to engine oil.

As a result, the level of ZDDP in today's engine oils has dropped from the original levels of 1,500 parts per million (ppm) that were allowed in API Service Classes SG and SH to 800 ppm, which are permitted in API Service Classification SJ and above. But it's still an effective sacrificial wear agent that can help keep your engine running smoothly and reliably, especially in engines with flat tappet camshafts or modified to produce more horsepower.