The quality of HD engine oils is assessed according to the API system (API - American Petroleum Institute). European manufacturers are also guided by this system.
Oils are designated by two letters. The first letter in the designation is the scope: S - service, suitable for carburetor engines; C - commercial, suitable for diesel engines. The second letter means quality in alphabetical order. The highest quality according to the API specification: SG for gasoline engines and CF for diesel engines.
Attention! Engine oils that are marked by the manufacturer as oils for diesel engines are not suitable for gasoline engines. There are oils that are suitable for both gasoline and diesel engines. In this case, both specifications are marked on the oil container (e.g. SG/CE).