API system - Engine oils
API (the American Petroleum Institute) originally divided engine oils up to Regular, Premium and HD oils. Regular indicated a straight mineral oil, Premium indicated that the oil contained a certain amount of protective additives and HD meant that the oil also contained a certain amount of detergent additives. This system is now out of date and has been replaced by a new API system. The new system is not concerned with providing any description of the various oil types but states the different types of operating conditions for both diesel engines and petrol engines. Primary consideration has thereby been given to the type of driving and engine design.
When the range of use of an oil is stated by using the letters of the API-system, these letters may be preceded by the words "API Service". For example, if an oil can be used for many different ranges of use, it is defined as "API Service CC, CD".
