API system - Engine oils
The official API text states the following for engine oils for use in both diesel and petrol engines:
Diesel engines
CA, CB
These are older quality designations which are no longer valid, and no detailed description of these qualities are given here.
CC
Typical for aspirated engines with high litre output and light supercharged diesel engines which work under moderately difficult to difficult conditions. Also includes individual petrol engines with extra high special demands. These oils provide protection against high temperature deposits in the above mentioned engines but also protection against corrosion and low temperature deposits in petrol engines.
CD
Typical for high speed, supercharged diesel engines with high output, which demand effective protection against wear and deposits. These oils provide protection against bearing corrosion and against high temperature deposits, irrespective of the quality of the fuel.
Petrol engines
SA, SB, SC, SD
These are older quality designations which are no longer valid, and no detailed descriptions of these qualities are given here.
SE
Typical for petrol engines of year model 1971 to 1979 and which work under the warranty terms of the engine manufacturers. Oils in this service class provide better protection against oxidation, high temperature deposits and corrosion in petrol engines compared with oils in classes SC and SD and can thus also be used when these are recommended.
SF
Typical for petrol engines in cars and certain trucks of year model 1980 and later which are maintained in accordance with the engine manufacturer's recommended service programme. The oils developed for the above mentioned service conditions are more stable where it concerns oxidation. They also provide better protection against wear, compared to those oils which only meet the minimum demands of class SE. In addition, they provide good protection against scaling, rust and general corrosion.
