what does friction modifier do?

Friction modifiers are polar molecules added to lubricants to minimize light surface contacts (sliding and rolling) that may occur in a given machine design. These are also known as boundary lubrication additives.

These molecules consist of a polar head (head) and an oil-soluble tail. The polar head attaches to a metal surface to create a cushion for the metal surface against another metal surface. The oil-soluble tails stand up like a carpet, vertically stacked besides each other in Nano-sized sheets covering the metal surface.

When the cushioned surfaces come in light contact with each other, these polar molecules hold up like a thick boundary film, making them softer than the metal surface and less prone to frictional wear. However, as the contact or load becomes heavier, these polar molecules are brushed off.

In engine oil and automatic transmission fluids, friction modifiers play a critical role in controlling torque application through clutch and band engagements. In limited-slip axle lubricants, they reduce the friction between gears and chains and eliminate chatter.

The use of friction modifiers has increased in recent years due to the drive for fuel economy. This has led to lower viscosity lubricants that require robust friction modifiers to minimize wear and friction.