What are the uses of lubricant oil?

When metal surfaces slide past each other friction causes heat. On a microscopic scale, metal surfaces look like huge mountain ranges and when one 'range' is scraped over another, mountain peaks are severed converting the required energy to local heat. Lubricating oil fills all the valleys keeping the sliding parts separated by a thin slippery oil film. Rapid movement still causes some friction and heat production and circulating oil (as in a car engine) carries the hot oil away to an oil cooler. Lubricating oils may also contain additives that increase the oils natural protection against corrosion. BTW most greases are a mixture of lubricating oil and soap and are often used where relative motion is slow and little heat is produced to be carried away. Of course grease may be used for rapidly rotating pump bearings, etc. where the heat melts the grease which then acts as oil. The bearing housing must carry away the expected heat load. Experts who study lubrication are tribologists (as in trials and tribulations or friction between people?).What are the uses of lubricant oil?
lubricationWhat are the uses of lubricant oil?
lubricants are soft and they can be mixed


with water or oil .


for example - graphite


Lubricants act as a go-between and reduces the kinetic friction


and static friction between two objects
of course to lessen the friction for smooth run of any machines, also to absorbed some heat, and also to have a clearance between two contact surfaces, best example is piston, it design to have clearance between the two surfaces.
one use, to lubricate
reduce or eliminate friction
T o lubricate, to lessen the friction of two bodies...
the answer is to reduce friction.


But what does the lubricant do?


It forms a layer between the two surfaces in contact. This layer having less friction can make the relative movement between the surfaces easy.