Extreme Pressure (EP) and Antiwear (AW) additives are chemical compounds that interact with the metal surface to form a protective sacrificial layer. EP & AW additives prevent or minimise wear in circumstances where the lubricant film thickness has degraded such as; Decrease in viscosity (e.g. due to temperature increase), reduction in speed and increase in bearing load.
AW agents create a sacrificial layer under normal operating conditions. EP agents are activated when exposed to high temperatures & pressures.