Functions of a Lubricant

1.    It decreases surface deformation, wear and tear, since the direct contact between the rubbing surfaces is avoided.
2.    It decreases loss of energy in the form of heat, in order that efficiency of machine is enhanced.
3.    It decrease expansion of metal by local frictional heat.
4.    It ignores seizure of moving surfaces, as the use of lubricant minimises the liberation of frictional heat.
5.    Consequently maintenance and running costs are decreased.
6.    Lubricant sometimes behaves as a seal. For instance, lubricant utilized between piston and the cylinder wall of an internal combustion engine behaves as a seal, thus preventing the leakage of gases under high pressure from the cylinder.