Function of lubrication:
Function of lubrication: a) Reducing frictional effect: the primary purpose of the lubrication is to reduce friction and wear between two rubbing surfaces. Two rubbing surfaces always produce friction. This continuous friction produce heat which causes wearing of parts and loss of power. In order to avoid friction, the contact of two sliding surfaces must be reduced as far as possible. This can be done by proper lubrication only. Lubrication forms an oil film between two moving surfaces. Lubrication also reduces noise produced by the movement of two metals surfaces over each other.
b) Cooling effect: the heat, generated by piston, cylinder, and bearing is removed by lubrication to a great extent. Lubrication creates cooling effect on the engine parts.
c) Sealing effect: the lubricant enters into the gap between the cylinder liner, piston and piston rings thus; it prevents leakage of gases from engine cylinder.
d) Cleaning effect: lubrication keeps the engine clean by removing dirt or carbon from inside of the engine with the oil.
 It should have a high viscosity index.
 It should have flash and fire points higher than the operating temperature of the machine.
 It should have high oiliness.
 The cloud and pour points of a good lubricant should always be lower than the operating temperature of the machine.
 The volatility of the lubricating oil should be low.
 It should deposit least amount of carbon during use.
 It should have higher aniline point.
 It should possess a higher resistance towards oxidation and corrosion.
 It should have good detergent quality.