Motor oil was just plain base oil in the early days of automotive lubrication
. Todays motor oils contain a wide variety of additives designed to improve their protection and performance capabilities. Motor oil additives serve three functions: protect metal surfaces, expanding the lubricants application range and extending the lubricants life.
Surface Protection Additives effectively address issues related to metal surfaces:
Anti-wear agents protect against friction, wear, scoring and seizure
Friction modifiers alter the oils coefficient of friction
Detergents keep surfaces free of deposits
Corrosion and rust inhibitors protect internal metal parts against corrosion and rust
Dispersants prevent insoluble contaminants from agglomerating by keeping them dispersed in the lubricant
Performance Additives:
Viscosity modifiers help reduce the rate of viscosity change when temperatures rise or drop
Seal swell agents help swell elastomeric seals by causing a chemical reaction in the elastomer
Pour point depressants modify was crystal formation and enable oils to flow at lower temperatures
Protective Additives extend the service life of the lubricant:
Anti-foamants reduce surface tension and speed the collapse of foam
Metal deactivators reduce the catalytic effect of metals on the oxidation rate, further slowing oxidation
Anti-oxidants reduce the oxidation rate by decomposing peroxides and terminating free-radical reactions