The primary purpose of lubrication is to reduce wear and heat between contacting surfaces in relative motion. While wear and heat cannot be completely eliminated, they can be reduced to negligible or acceptable levels. Because heat and wear are associated with friction, both effects can be minimized by reducing the coefficient of friction between the contacting surfaces. Lubrication is also used to reduce oxidation and prevent rust; to provide insulation in transformer applications; to transmit mechanical power in hydraulic fluid power applications; and to seal against dust, dirt, and waste.

Lubricants play a key role in machinery element safety. Their main tasks are

• To keep moving parts apart from each other,
• To take heat out of the contact by their through pass,
• To keep surfaces clean,
• To transport functional additives toward the surface
• To transfer power in the application (hydraulic, automatic transmission, breaks).