The aim of lubrication is to decrease friction by separating two surfaces, to ease movement by lubricating surfaces, to avoid corrosion and oxidation by generating film on the surface and to avoid oil-fuel mixture in engines.

Viscosity is the resistance of fluids against flowing and is the most distinct and important quality of fluids. Viscosity is a vital factor to be taken into consideration by the consumer at every stage of lubrication.

Attention should be paid to issues whether engine oil is hot or not, that the vehicle is in stop position and on a flat surface, whether used oil in engine pan is empty and whether pan bung is mounted properly.

The main reason is the technology used in the engine. In new engines, metals are designed more closely to provide higher performance. This leads to oil loss. Further, using oil with inappropriate viscosity in vehicle oil pan, using oil with inappropriate performance in vehicle and operating the vehicle at high speed constantly could be counted as reasons for oil loss in an engine.

One of the duties of engine oil is to clean. A qualified engine oil incorporates soot particles in engine after separating them and prevent them from sticking on metal surfaces due to the additives in its content. It cleans soot particles adherent on metal surfaces with cleaning agent. Therefore, engine oil becomes dirty and its color turns black. If the motor oil is dirty, it is doing its job well.

To understand for certain whether motor oil has perished, the oil should be analyzed physically and chemically under laboratory conditions.

Firstly, the oil to be added should not exceed normal oil level. If it exceeds, froth and heating in the system can occur. Oil to be added should have the same viscosity grade and be in the same API class; mineral oil and synthetic oil should not be mixed.

Synthetic based oils are oils produced with chemical methods. They are produced to lubricate under conditions where other oils with natural structure cannot function. Synthetic based oils are resistant to higher or lower temperatures and higher pressure compared to minerals.

As raw material of synthetic oil is produced through very complex processes with advanced technology, it costs higher than mineral oils. That influences the price of the product.

Performance of an oil can be figured out by API and ACEA values on its package. In oils developed up to today, SL (July 2001) in gasoline class and CI – 4 (2002) in diesel class indicate the highest API performance level. ACEA performance classes are indicated for passenger car by A3, for diesel light commercial vehicles by B3 and for heavy commercial vehicles by E4.

API (American Petroleum Institute) expresses the performance of oil. ‘ S ‘ means it will be used in vehicles with spark plug ignition and the letter ‘ C ‘ means it will be used in vehicles with pressure ignition.

In API SJ / CF example, as ‘ S ‘ is the prominent letter, this means it is recommended to use that oil in gasoline-powered vehicles. ‘ J ‘ letter after ‘ S ‘ indicates that the oil is for gasoline-powered vehicle class. This oil can conveniently be used as CF class oil in diesel vehicles.

‘W’ comes from the word ‘winter’. 0W means a very thin oil carrying the qualities of ‘zero’ number oil under winter conditions.

It is the API classification used for gear oils. In GL-5, there are more overpressure additives and it is generally used under heavy work conditions. Unless otherwise specified, GL-5 should not be used in places where GL-4 is recommended. Because the sulphide in overpressure additive which is present excessively in GL-5 corrodes yellow metals.

Oil change kilometers of vehicles are determined only by vehicle manufacturers. It can be said that synthetic oils are more resistant than mineral oils. Therefore, whether synthetic or mineral oil is used affects engine performance and protection directly. However, if oil change kilometer is changed without approval of manufacturers of the vehicle, expected performance and protection might not obtained.

Foaming occurs due to surge in oil pan and the oil hitting surfaces within engine as the vehicle constantly moves.

Should there be no defoaming additives or an insufficient quantity, bubbles in the foam blow out during any contact. Therefore, metal friction and corrosion begins.

The type of foaming known generally is the image resembling to cream or mayonnaise. This is not foaming. If water is mixed with oil or as it was in vehicles with old technology, if oil vapour cannot move out and then condense due to day-night temperature difference and mixes in oil, this image emerges.

It is important to separate foaming from creaming, that does no harm to engine.