The aim of lubrication is decreasing friction by seperating two surfaces from each other , simplifying movement by providing surfaces slickness, preventing corrosion and oxidation by forming film and inhibiting mixing of oil and fuel in the engine.

* Provides quick start-up at low temperatures.
* Provides minimum loss of oil at high temperatures.
* Cleans the engine through modern additives.
* Prevents oxidation and corrosion
* Less sludge and deposit in the engine through low ash level
* Provides fuel economy.
* Lenghthens life of the catalytic convertors by decreasing emission.
* Lengthens life of the engine.
* Provides working of valve system seamlessly.

Selection of oil must be done according to some criterias. These are the criterias;
1. Values of viscosity and performance classifications that take place in vehicle operating
manual is considered. The oils meeting automative manufacturers’ needs should be selected.
2. According to type and technology of the engine.
3. According to season conditions (for instance; selecting synthetic oils in very cold seasons.)
4. According to type and quality of fuel. It is determined according to needs of performance or fuel economy (synthetic oils provide beter performance and fuel economy than mineral oils)

The time intervals for oil change and and service is determined according to country that vehicle is used and its conditions by the manufacturer. Users have to comply with the rules that manufacturers determined according to mineral or synthetic independent from usage of oil.
If change over time of the oil is delayed, it may cause failing of specific properties of the oil.
As a result of this, some problems may occur;
* More wear
* Increase in oil and fuel consumption.
* Decrease in performance of the engine.
* Fever in the engine.
* Working of engine equipments dry.
* Incresase in cost of motoring.
* Wear in turbo bearing if it is present.
* Decrease in lifetime of catalytic convertors.