The two objects resist each other in their basic state and this is called friction. To reduce the effect of this friction, the surfaces of the objects must be lubricated. For this reason, the lubrication process and the selection of the oil in the engines are of the utmost importance. Although lubrication in engines is generally applied to reduce friction, there are different reasons for its use. These reasons;

• Reduction of wear to prevent mineral contacts

• Sealing between piston and cylinder

• Remove excess heat from friction and cool pistons

• Prevent corrosion by providing protection

• It serves to prevent and clean up the residues of combustion.

The types of lubrication of the engines are as follows.

• Impact lubrication

• Pump and impact lubrication

• Pressure lubrication

• Full pressure lubrication

When selecting lubricating oil to be used to lubricate your engine, you must observe the following conditions.

• First of all, the engine oil must be of constant viscosity and suitable.

• It should be able to provide good protection even under difficult conditions by adhering very well to the lubricated surfaces.

• It must have high film strength and withstand high film pressures in the bearing parts.

• The selected oil must not cause corrosion in any way and must be capable of protecting the engine parts.

• It must be able to be sucked in by the engine's oil pump, even at low temperatures and at a low pour point.

• When the air is combined with water and fuel, it should not foam and precipitate.

• It should be able to clean the wastes that may occur as a result of combustion.

• It should be able to prevent and distribute foreign substances that may be mixed into the oil.

• It must not be explosive or toxic.

• Economical and safe.

Lubrication and oil selection in engines are extremely important and need to be addressed. If the engines are not properly lubricated with the appropriate lubricants, they may cause greater problems.