Classifying engine oils based on performance levels
American Petroleum Institute with acronym of API has classified engine oils into two groups, S (station) for petrol driven engines, and C (commercial) for diesel engines according their quality levels. These letters are followed by second letter that indicates lubricant performance. Gasoline engine oils begin from the lowest quality level SA, the higher quality levels are specified by changing the second letter in Latin letters order. These days the last and the highest quality level in this group is SN. Diesel engine oils begin from the lowest quality level that is CA, the higher quality levels are specified by changing the second letter in Latin letters order. Nowadays the last and the highest quality level is CJ-4.
SA---SB---SC--- SD---SE---SF---SG---SH---SL---SM---SN
CA---CB---CC---CD---CE---CF-4---CG-4---CH-4---CI-4---CJ-4
Lower quality <---------> Higher quality
In addition to API, other institutes such as USA military (with the abbreviation of MIL-L) and union of European car manufacturers (with abbreviation of CCMC that has regrouped to ACEA) has developed new classifications for the application of engine oils.
For selecting suitable engine oil, referring to automobile manual specifies performance level and viscosity of oil, and that is enough to refer to oil drains and select engine oil with similar quality level and viscosity which is in a standard container and packaging and has been produced in a reliable company, the consumer can get the maximum confidence of oil optimum operation in engine. In this way, the automobile manual is the best guide.
Category
status
Quality Specifications
SA
Obsolete
For older engines; no performance requirement. It is just base oil, does not have additives or including a little pour point dispersant and anti-foam.
SB
Obsolete, is introduced in 1930
For older engines. Use only when specifically recommended by the manufacturer. Including a little anti-oxidation and anti-wear.
SC
For model year 1964-1967 and older gasoline engines
Including anti-wear and anti-corrosion additives and some detergent to control deposits due to engine working in high and low temperatures
SD
For model year 1968-1970 and older gasoline engines
Is like SC oil, including a bit more additives and anti-rust
SE
For model year 1971-1979 and older gasoline engines
Is like SC and SD, with more detergency and more stability against oxidation, corrosion and rust. Can be used instead of SC and SD.
SF
For model year 1980-1988 and older gasoline engines
Is like SE oil, with more oxidation stability and better anti-wear property than SE.
SG
For model year 1989-1993 and older gasoline engines
Compared with former oils has better anti-oxidation and anti-wear, and has SF additives too, so can be used instead of it.
SH
For model year 1994-1996 and older gasoline engines
Including the SG additives, and has anti-oxidation anti-corrosion and anti-rust properties. This oil is tested by Chemical Association Manufacturers (CMA) about environmental issues.
SJ
According to car manufacturer is suitable for using in model year 1997-2001, and is currently in use.
Is including all the suitable additives for engine oil, This oil is tested by American Chemistry Council (ACC) and has high quality level.
SL
According to car manufacturer is suitable for using in model year 2002-2004, and is currently in use
Is including all the suitable additives for engine oil like SJ, has higher quality level than SJ and can be used wherever SJ and lower levels are recommended. This oil environmentally has good condition.
SM
Is recommended for the newest gasoline engines model year 2005 and over
Is including all the suitable additives for engine oil like SL. As this oil has all the additives of SL and SJ levels, so can be used wherever using of SL and SJ are recommended.
SN
Is the newest quality level introduced by API, is recommended for use in the newest gasoline engines.
Includes the most complete additive package. It is the newest quality level introduced by API which has not applied publicly yet in many countries. As this oil has all the additives of SM, so can be used wherever using of SM are recommended.