This explains the chemical mechanism: https://en.wikipedia.org/wiki/Extreme_pressure_additive https://en.wikipedia.org/wiki/Extreme_pressure_additive An import

This explains the chemical mechanism: https://en.wikipedia.org/wiki/Extreme_pressure_additive https://en.wikipedia.org/wiki/Extreme_pressure_additive An important property is that when localized hot-spots appear on metal surfaces due to friction, the heat causes a chemical reaction that bonds the molecule to the metal preventing further wear. Organophosphates like ToCP do this at higher temperatures than some less toxic compounds, presumably important in jet engines. So they're not just mixing in random poisons for no reason.