Friction Modifier

Definition - What does Friction Modifier mean?

A friction modifier is a fuel additive commonly used in boundary lubricant applications to reduce the coefficient of friction and improve the lubricity and energy efficiency. They are polar chemical compounds having high affinity for metal surfaces and possessing long alkyl chains.

This additive is a key component of modern engine oils, and plays a vital role by reducing friction in key metal-to-metal contact points in engines and transmissions.

Friction modifiers are also known as boundary lubrication additives or friction reducers.

Corrosionpedia explains Friction Modifier

Friction modifiers are oil-soluble chemicals which are used as additives in lubricating oils for internal combustion engines and transmissions. In addition to boosting fuel economy by reducing friction, they can also prevent metal scoring, reduce engine wear and noise, and help to prevent micropitting of metal surfaces when used in industrial gear lubricants.

Friction modifiers typically have a water-soluble end (head) and an oil-soluble end (tail). When used as a lubricant additive, the water-soluble end of the molecule finds a metal surface and attaches itself. This provides a sacrificial liquid coating on the metal, which serves to minimize friction as a result of metal-to-metal contact.

Friction modifiers are commonly used in gasoline engine oils, and are added to fluids for:

  • Automatic and manual transmissions
  • Tractor hydraulic systems
  • Power steering
  • Shock absorbers
  • Metalworking applications

In automatic transmission fluids and limited-slip axle lubricants, friction modifiers control torque application through clutch and band engagements.

Although friction modifiers are key additive components, they are only present in small quantities in the fluid. Most friction modifiers act by creating a smooth, associative film across the surface to reduce sliding and/or rolling friction. The lubrication needs must be carefully balanced, for friction modifiers must operate in the presence of other additives such as antiwear agents, which tend to increase the friction.

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