Engine oils have been being produced by mixing base oils obtained by means of petroleum refining and/or base oils of polymeric structure obtained synthetically, and the additives in proportions to meet the specific standard, specifications.

These are engine oils produced by blending base oils obtained by distillation of crude oil and additives like detergent, dispersant, viscosity improver, wear inhibitor etc.

Synthetic based oils are the oils obtained by chemical means in the laboratory. They are produced for the purpose of lubrication where other oils, having natural structure, fail to work. Synthetic based oils offer better performance and long term use than minerals, and resistant to higher or lower temperatures and high pressure. Since synthetic oils are produced by advanced technology by going through intense process, their cost is high.

Semi-synthetic oils are a mixture of these two and the performance that they offer is between these two oils. In general, they are obtained by mixing 20-30% synthetic oil in 70-80% mineral oil.

To minimize friction and wear between engine parts, to prevent corrosion, to help cooling, and to balance heating in the engine, to control sediment and deposit formation by cleaning engine with detergent dispersant additives it contains, to sediment and deposit formation, to improve engine performance, to protect the engine components and extend engine life.

Only vehicle manufacturers determine the millage of changing engine oil. It can be said that synthetic oils are much more resistant than minerals. Therefore, used oil being synthetic or mineral, directly affects engine performance and protection. However, if the millage of changing engine oil is extended without the approval of vehicle manufacturers, expected performance and protection may not be taken.

The viscosity is simply the measure of an oil thiskness. The viscosity index shows us how much is oil become thin when it is exposed to heat. The higher figure means oil becomes less thin when exposed to heat. Viscosity index also shows how oil will act under certain conditions. Chosing the viscosity of the oil to be used should be performed by considering the recommendation of the equipment manufacturer and climatic conditions at the place of use.

The viscosity classification of engine oils is made according to the SAE (Society of Automotive Engineers) classification. SAE classification, apart from others, classifies the oil according to its viscosity at low and high temperatures. In SAE classification, the figure consists of two digits separated by the letter “W”. W means winter, and shows the viscosity of the oil in low-temperature. For example; like 10W in 10W-40. Since the lower figure means the thinner oil, this also shows us how fluent the oil will be at low temperatures and how easily the engine will start. Second figure gives high temperature viscosity of oil. For example; like 40 in 10W-40. The higher figure means the more viscous oil while it is hot, in other words, thicker.

Automotive oils have been classified by various organizations and initials of these organizations’ names have been used in front of the test numbers applied to oils. These classes determine the performance of the oil.

The expansions of these abbreviations are as follows.

• SAE: Society of Automotive Engineers
• API: American Petroleum Institute
• ILSAC: International Lubricant Standardization & Approval Committee
• ACEA: Association of European Automotive Manufacturers
• MIL: US Military Oil Specifications
• JASO: Japan Automobile Standards Organization

The most appropriate classifications are API, ACEA and ILSAC classifications. In order to understand the performance of oil, API and ACEA values in the packaging are checked.

One of the most valid criteria in quality classification of engine oils is the API. Classification is made with two letters. The first letter indicates which oil is appropriate for gasoline-powered engines (S) and diesel (C) engines; while the second letter shows the performance value of the oil in the same group. For example; API SH / CF. The letter “S” shows to be used in spark plug ignition vehicles (spark ignition) and the letter “C” shows to be used on compressed ignition vehicles. Performance classification is made, being the lowest A in both groups, between A-M for gasoline-powered engines, and C-I for diesel engines (Such as SA, SB, ........ SH, SJ). As the letters, coming after the letters S and C, proceed in alphabetical order, the quality of engine oil increases. If you see an ignition signal indicating “API SM / CF” on your crankcase, this means that oil can be used in all gasoline-powered and diesel engines.

European Automobile Manufacturers Association ACEA (Association des Constructeurs Europens d'automobile), was put into practice a new engine oil quality classification that supersedes the classification of the former CCMC partnership in 1996. According to this classification, gasoline-powered engine oils have been indicated by the letter A, light diesel engine oils by the letter B, and heavy-duty engine oils by the letter E. The quality classification has been rearranged in November 2004. According to this, the classification of gasoline-powered engine oils and light duty diesel engine oils were combined and has been indicated by the letter A/B; while special filter equipped gasoline- powered engine oils and light diesel engine oils have been indicated by the letter C and heavy-duty engine oils by the letter E.