Friction modifier is a special additive that helps to reduce friction between metal surfaces in the engine and other moving parts of the machine. The main function of this type of additive is to create a cushion between surfaces that would otherwise rub together and wear each other out, thus minimising frictional losses and increasing energy efficiency.

Traditionally, this was accomplished by lowering lubricant viscosity to minimize hydrodynamic shear and churning losses but now a growing concern about climate change has led to a resurgence of interest in friction modifier additives (OFMs). Each OFM molecule consists of 2 parts, a polar head which adheres to polar surface metals and an oil soluble tail which extends out into the lubricating oil. The tails of each molecule overlap each other and are held in place by the lateral van der Waals force, creating an organic monolayer which acts like a buffer between rubbing surfaces.

OFMs are classified as mild anti-wear additives which minimise light surface contact and are primarily used in engine oils and transmission fluids. When heavier loads are present and more than just boundary lubrication is needed, then stronger anti-wear additives such as Zinc dialkyldithiophosphate (ZDDP) are employed.

When mixed into a lubricant, the OFM molecules circulate around the components in the engine and coat them with an invisible layer of Molybdenum disulfide which acts as a soft, slick barrier to prevent contact between surfaces. This reduced friction results in less heat being generated which, in turn, decreases the rate of oxidation of the lubricant and extends its life. Less heat also reduces the stress on the metal components which could potentially cause cracking and abrasions.