The most well-known international classification of motor oils according to the field of use and the level of exploitation properties is the API (American Petroleum Institute) classification. Since the implementation date (1947) this classification has been completed countless times, although the principle of dividing oils into 2 categories (S and C) has been preserved until now.
In this classification system, engine oils are denoted by the 2-letter symbol. The first letter indicates the category: the category “S” (Service) includes the oils for 4-stroke petrol engines, the category “C” (Commercial) includes the oils intended for diesel car transport engines, for construction equipment other than road and agriculture. Universal oils are those that can be used to lubricate gasoline and diesel engines. The second letter indicates the oil group according to the operating characteristics. The farther the letter is from the beginning of the Latin alphabet, the higher the degree of exploitation characteristics of the engine oil.
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