Engine oils are produced from base oils which are made by refining the crude petrol or/and polymeric base oils which are made in laboratories synthetically. Also special additives are added to base oils in specific amounts in order to meet desired specifications.
These kinds of oils are produced by adding special additives like detergent/ dispersants, viscosity improvers, wear and corrosion preventives etc. to base oils produced by distillation of crude petrol.
These kinds of oils are artificially produced in laboratories by chemical processes. Synthetic motor oils are used as a substitute for engine oils refined from petroleum when operating in extreme temperature and pressures, as they generally provide better performance, longer usage time, superior mechanical and chemical properties than those found in traditional mineral oils. Since synthetic engine oils are produced through high-tech operations their costs are relatively higher than mineral and semi-synthetic oils.
Semi-synthetic engine oils are mix of mineral and synthetic oils and their performances are also between those two. They are generally produced by mixing 70-80% mineral oil with 20-30% synthetic oil.
Engine oils are briefly used to lubricate the moving parts of a motor. Engine oil helps to reduce friction and wear, to cool motor and stabilize motor temperature. Engine oil also prevents corrosion, sludge formation and by the help of detergent/dispersant additives, it cleans motor, increases motor performance, helps fuel economy, protects motor parts and extends motor life.
AAMA (American Automobile Manufacturer’s Association) and JAMA (Japan Automobile Manufacturer’s Association) together established a new organization ILSAC which identifies a new engine oil classification containing fuel economy parameter of petroleum engine oils. Since 1994 classifications are made as GF-1, GF-2, GF-3 and GF-4.
Viscosity is a fluid’s resistance to flow under gravity measured in mm2/s or Centistokes (cSt), and expressed at a certain temperature. Viscosity is simply defines the thickness of the oil. Viscosity index is a scale used to show the magnitude of viscosity changes in lubricating oils in response to the changes in temperature. In case of a high viscosity index, a lubricant’s viscosity changes (decreases) less as the temperature increases. Viscosity index also shows the behavior of lubricants under certain conditions.
Engine oil classifications are made according to SAE (Society of Automotive Engineers). According to SAE, engine oils are classified according to their viscosity values at low and high temperatures. In this classification there are 2 numbers separated by letter “W” (initial of word Winter) and this shows the viscosity of the oil at low temperature, such as 10W in SAE 10W/40. As this number is lower, the oil is thinner and more liquid at low temperatures so it provides easier engine start-up. Second number shows viscosity of the oils at 1000C, such as 40 in SAE 10W/40. As this number is higher, the oil is thicker at high temperatures.
Most common classifications are API, ACEA and ILSAC. In order to identify engine oil’s performance, API and ACEA levels on the package should be checked.
Oil change intervals are determined only by motor vehicle manufacturers. Synthetic oils may be said to be more durable than mineral oils. Thereby, engine performance and protection is directly related to the engine oil being of mineral or synthetic nature. However, if the oil change kilometer is extended without approval of the vehicle manufacturer, then the expected performance and protection can not be foreseen.
API is one of the most common and acceptable classification for engine oils. Classification is made by 2 letters; for example API SL/CF; first letter (S: spark ignition) is designated for petroleum cars and (C: compressed ignition) is designated for diesel engine cars. Second letters following “S” and “C” indicate the performance level of the motor oil; higher performance is indicated according to the alphabetical order. For example API SL is more update and higher performance level than API SG; likewise API CF and CC have same situation. Currently for petroleum engine cars SN, and for diesel engine cars CJ is the latest performance levels. An inscription such as “API SJ/ CF” denotes that the engine oil can be used in both petroleum and diesel engine cars.
ACEA (Association des Constructeurs Européens d’ Automobile) replaced CCMC’s old classification with the new ACEA classification in 1996. According to this classification, petroleum engine oils are classified by letter “A”, light diesel engine oils are classified by letter “B” and heavy diesel engine oils are classified by letter “E”. In November 2004 this classification was revised and petroleum and light diesel engine oils were classified by letter A/B, petroleum and light diesel engine oils with special filters are classified by letter “C” and heavy diesel engine oils are classified by letter “E”.