friction modifiers in motor oil help reduce friction among metal surfaces to prevent damage and improve the performance of your car. They're especially important in engine lubricants as they help improve power and fuel economy. In fact, this is one of the reasons why many modern cars have friction modifiers added to their oil.

The main function of friction modifiers is to lower the viscous drag of the lubricant film that separates the moving parts of your engine, reducing friction and boosting the efficiency of your vehicle. They work by coating the piston rings and cylinder walls with a thin layer of molecules, which then helps improve lubricant shear characteristics during relative motion. The resulting molecule film can also help to protect the lubricant from degradation by oxidation and other chemical effects.

There are several different types of friction modifiers, which act differently under specific shear conditions. For example, oil soluble organomolybdenum additives are best suited to severe reciprocating sliding conditions while functionalised polymer friction modifiers perform well in rolling-sliding contact tests. When two different friction modifiers are combined in solution, the results are often either synergistic or antagonistic.

In addition to friction modifiers, engine oils also contain anti-wear additives. Zinc dialkyldithiophosphate (ZDDP) is a common and effective anti-wear agent that works by reacting with the metal surface to form a molecular protective barrier that prevents metal to metal contact. It is also highly effective at lowering friction between the piston ring and the cylinder wall.