The primary purpose of a lubricant is to reduce friction between two surfaces. Lubricity describes the reduction in friction caused by the lubricant. There are many instances in which the base oil in the industrial grease or oil may not have the right lubricity. The friction modifiers are added to increase or decrease the lubricity of the base oil, thereby meeting the demand of the application.
Friction modifiers are compounds that modify the coefficient of friction of lubricants. In other words, these compounds alter the amount of energy needed to cause two surfaces to move past one another. There are many kinds of friction modifiers. Some friction modifiers increase lubricity to improve efficiency. Others lower lubricity to give mechanical components more traction.
Lowering the friction within a combustion engine allows components to move more smoothly and thereby improving fuel economy. In automatic transmissions, the purpose of the friction modifier is to increase friction as to prevent slippage during transitions.
There are many lubrication applications in which a certain amount of traction friction is required for equipment to operate properly. The friction modifiers used in these applications are not intended to increase or lower friction but to cause the lubricant to act differently depending on the shear conditions.
The friction modifier smoothens the transition from a dynamic condition to a static condition like what happens during a gear change or the engagement of a clutch.