European oil manufacturers classify their products according to the ACEA (Association dec Constructeurs Europeens d'Automobiles) system, which takes into account the specific features of European engine technology. Depending on their quality, oils for gasoline engines are divided into groups from A1-96 to A3-96 according to the ACEA classification; motor oils for diesel engines are divided into groups from B1-96 to B3-96. The marking AZ and, accordingly, B3 indicate the highest quality oil.
The quality of motor oil from American manufacturers is designated by the API system (American Petroleum Institut). The oil characteristic is given, depending on the circumstances, by two letters. The first letter indicates the area of application: S (Servicej oil is used in gasoline engines. With (Commercial) — oil is used in diesel engines. The second letter indicates the quality in alphabetical order. According to the API specification, the highest quality is SJ oil for gasoline engines and CF oil for diesel engines.
Note: Motor oils that are designated by the manufacturer as oils for diesel engines only are not suitable for gasoline engines. However, there are oils that can be used in both gasoline and diesel engines. Both specifications are indicated on the packaging of such oils (for example, ACEA AZ-96/VZ-96 or API SH/CD). BMW has set different standards for its engines and divides motor oils into long-life oils (Longlife-Ole) and special oils (Spezialole).