See Lubrication

That portion of a lubricant that volatilized in use or in storage. Widely used test methods are ASTM D972 and D2595.

Extreme pressure (EP) additives are additives that provide added load carrying capacity under boundary lubrication conditions. EP additives chemically react with the metal surface under conditions of high load and elevated temperature, forming a chemically bonded lubricating film.

The ability of a lubricant to reduce scuffing, scoring and seizure that can occur when highly-loaded moving surfaces are in contact. High loads are applied to moving surfaces that are in contact. Commonly used laboratory test measurements of EP level are Timken OK Load (ASTM D2509 (grease) and D2782 (oil)) and Four Ball Weld and Load Wear Index (ASTM D2596 (grease) and D2783 (oil)).