API Engine Service Classifications

The American Petroleum Institute (API) engine oil classification system was set up as a joint effort by API, ASTM (American Society for Testing and Materials) and SAE (Society of Automotive Engineers). The letter classification system is a method of classifying engine oils according to their performance characteristics, and relating this to their intended type of service.

The API system currently includes service classifications for service stations/spark ignition engines (“S” series), for commercial applications/compression ignition engines ("C" series), and for energy conserving engine oils ("EC" series). It is an "open-ended" system which allows for the addition of new designations with little change to existing ones.
 

“S” Service Station/Spark Ignition Engine Classifications:

Only two API "S" Service Classifications, categories SJ and SH (restricted usage), are current. The API decided to move directly from API Service Classification SH to SJ in order to avoid confusion with the abbreviation SI, which is used for the Système International d’Unitès (International System for Units) and "spark ignition". The remaining categories are obsolete due to the introduction of higher performance categories, or the non-availability of test methods:

 

SJ for 1996 Gasoline Engine Warranty Maintenance Service

Service typical of gasoline engines in current and earlier passenger car, van and light truck operation under vehicle manufacturers' recommended maintenance procedures. First available from 15 October, 1996, oils of this category exceeded the minimum performance requirements of API Service Category SH with a slightly different simulated distillation and evaporation loss, plus met the requirements of bench tests for wet filterability, gelation index, high temperature foaming and high temperature deposits. API Service Category SJ also introduced a limit on phosphorus content of 0.1 0 mass %. API Service Category SJ may be used where API SH, SG and earlier categories have been recommended.

Engine Test Requirements: IID, IIIE, VE, L-38 (plus some bench testing requirements).
 

SH for 1994 Gasoline Engine Warranty Maintenance Service (currently restricted usage)

Service typical of gasoline engines in current and earlier passenger car, van and light truck operation under vehicle manufacturers' recommended maintenance procedures. First available 1 January 1994, oils in this category exceed the minimum performance requirements of API Service Category SG in the areas of deposit control, oil oxidation, wear, rust and corrosion. Engine oils Meeting API Service Category SH have been tested in accordance with the Chemical Manufacturers Association (CMA) Code of Practice, and may be used where API Service Category SG and earlier categories have been recommended.

Engine Test Requirements: IID, IIIE, VE, L-38 (plus some bench testing requirements).
 

SG for 1989 Gasoline Engine Warranty Maintenance Service (Obsolete)

Service typical of gasoline engines in passenger cars, vans and light-duty trucks, and some diesel engines beginning with 1989 models operating under manufacturers’ recommended maintenance procedures. Oils developed for API Service Classification SG provided improved control of sludge and varnish, oil oxidation and engine wear relative to engine oils developed for previous categories. These oils also provide protection against rust and corrosion. Oils meeting API Service Category SG may be used when API Service Categories SF, SE and earlier categories are recommended.
 

Engine Test Requirements: IID, IIIE, VE, L-38, 1-H2.
 

SF for 1980 Gasoline Engine Warranty Maintenance Service (Obsolete)

Service typical of gasoline engines in passenger cars and some trucks beginning with 1980 models operating under manufacturers' recommended maintenance procedures. Oils develop for this service provided increased oxidation stability and improved anti-wear performance relative to engine oils that met the minimum requirements for API Service Category SE. These oils also provided protection against engine deposits, rust and corrosion. Oils meeting API Service Category SF may be used when API Service Categories SE, SD or SC are recommended.

Engine Test Requirements: IID, VD, L-38.
 

SE for 1972 Gasoline Engine Warranty Maintenance Service (Obsolete)

Service typical of gasoline engines in passenger cars and some trucks beginning with 1972 a certain 1971 models operating under manufacturers' recommended maintenance procedure Oils designed for this service provided more protection against oil oxidation, high-temperate engine deposits, rust and corrosion in gasoline engines than oils that satisfied API Engine Service Categories SD or SC and may be used when either of these categories are recommended.

Engine Test Requirements: I/C or 11D, 1/IC or IIID, VC or VD, L-38.
 

SD for 1968 Gasoline Engine Warranty Maintenance Service (Obsolete)

Service typical of gasoline engines beginning with 1968 models. Of little relevance to modern gasoline engines. Superseded by API Service Category SE in 1972.

Engine Test Requirements: IIB, IIIB, IV, VB, L-38, L-1 or 1-H.
 

SC for 1964 Gasoline Engine Warranty Maintenance Service (Obsolete)

Service typical of gasoline engines in 1964 through 1967. Of little relevance to modern gasoline engines. Superseded by API Service Category SD in 1968.

Engine Test Requirements: IIA,IIIA, IV, V, L-38, L-1.
 

SB for Minimum-Duty Gasoline Engine Service (Obsolete)

Oils meeting this service provided only mild antiscuff capability, and some resistance to oxidation and bearing corrosion. Oils of API Service Category SB should not used in any engine unless specifically recommended by the manufacturer.


Engine Test Requirements: L-4 or L-38, IV.
 

SA formerly for Utility Gasoline and Diesel Engine Service (Obsolete)

Oils for such mild service that the category had no performance requirements. Oils of API Service Category SA should not be used in any engine unless specifically recommended by the manufacturer.

Engine Test Requirements: None.
 

“EC” Energy Conserving Classifications:

Only one Energy Conserving "EC" Classification is current.


Energy Conserving in conjunction with API Service Category SJ

API Service Category SJ oils categorized as Energy Conserving are formulated to improve the fuel economy of passenger cars, sports utility vehicles, vans and light-duty trucks powered by gasoline engines. These oils have produced a fuel economy improvement of 1.4% or more (0W-xx and 5W-xx viscosity grades), or 0.5% or more (10W-xx and all other viscosity grades) in the Sequence VIA test, when compared with the standard reference oil used in the test.


Energy Conserving II in Conjunction with API Service Category SH (Obsolete)

API Service Category SH engine oils categorized as Energy conserving II are formulated to improve the fuel economy of passenger cars , sports utility vehicles, vans and light duty trucks gasoline engines. These oils have produced a fuel economy improvement of 2.7% or more in Sequence VI test, compared with the standard reference oil used in the test.
 

Energy Conserving in conjunction with API Service Category SH (Obsolete) API Service Category SH engine oils categorized as Energy conserving are formulated to improve the fuel economy of passenger cars , sports utility vehicles, vans and light duty trucks gasoline engines. These oils have produced a fuel economy improvement of 1.5% or more in Sequence VI test, compared with the standard reference oil used in the test.
 

“C” Commercial Classifications:

Four API "C" Service Classifications are current. A new proposal is being prepared for the heavy-duty engine oils which will be required for engines meeting 1998 emission requirements.
 

CG-4 for Severe-Duty, Four-Stroke-Cycle Diesel Engine Service

API Service Category CG-4 describes oils for use in high speed, four-stroke-cycle diesel engines used in both heavy-duty on-highway (0.05% weight sulfur fuel) and off-highway (less than 0.5% weight sulfur fuel) applications. CG-4 oils provide effective control over high temperature piston deposits, wear, corrosion, foaming oxidation stability and soot accumulation. These oils are especially effective in engines designed to meet 1994 U.S.A. exhaust emission standards and may also be used in engines requiring API Service Categories CF-4, CE and CD.

Engine Tests Requirements: 1N, T8, IIIE, L-38, GM6.2L (plus some bench testing requirements).
 

CF-4 for Severe-Duty, Four-Stroke-Cycle Diesel Engine Service

Service typical of certain high-speed turbocharged and supercharged, four-stroke-cycle diesel engine since 1990. API Service Category CF-4 oils exceed the requirements of the API Service Category CE, and provide improved control of oil consumptions and engine deposits. Oils meeting API Service Category CF-4 may be used when API Service Categories CE and CD are recommended for diesel engines.
 

EngineTests Requirements: 1 K, L-38, T-6, T-7, NTC-400.


CF-2 Two-Stroke-Cycle Diesel Engine Service

API Service category CF-2 denotes service typical of two-stroke-cycle engines requiring highly effective control over cylinder and ring-face scuffing and deposits. Oils designated for this service have been in existence since 1994 and may also be used when API Service category CD-II is recommended. These oils do not necessarily meet the requirements of CF or CF-4 unless passing test requirements of these categories.

Engine Test Requirements: 1M-PC, 6V-92TA, L-38.


CF for Indirect-Injection Diesel Engine Service

API Service category CF denotes service typical of indirect-injected diesel engines, and other diesel engines which use a broad range of fuel types including those using fuel with higher sulfur content, for example over 0.5% weight. Effective control of piston deposits, wear and copper containing bearing corrosion is essential for these engines which may be naturally aspirated, turbocharged or supercharged. Oils designated for this service have been in existence since 1994, and may also be used when API Service Category CD is recommended.

Engine Test Requirements: 1 M-PC, L-38.


Proposed Service Classification for Diesel Engine Oils:

PC-7 for Severe-Duty, Four-Stroke-Cycle Diesel Engine Service
Service Classification proposed for introduction in 1998 for high-top-ring, low emission, heavy-duty, four-stroke-cycle diesel engines operating on low sulfur diesel fuel. It is proposed that oils of this category will assure adequate protection in 1998 engines, and provide improved control of oil consumption, valve train wear and engine deposits.
Also under discussion is an Extended Service Interval (ESI) designation. API ESI is intended to be an addition to PC-7 oils, similar to the use of API EC with passenger car motor oils.


Obsolete Service Classification for Diesel Engine Oils:

CE for 1983 Diesel Engine Service (Obsolete)

Service typical of certain turbocharged and supercharged heavy-duty diesel engines manufactured since 1983 and operating under high-load conditions for both low and high speed operation. Oils designed for this service may be used where API Service Category CD is recommended for diesel engines.

Engine Test Requirements: 1-G2, L-38, T-6, T-7, NTC-400.
 

CD-II for Severe-Duty Two-Stroke-Cycle Diesel Engine Service (Obsolete)

Service typical of two-stroke-cycle diesel engines requiring highly effective control over wear and deposits. Oils designed for this service also meet all the requirements of API Service Category CD.

Engine Test Requirements: 1-G2, L-38, 6V-53T.
 

CD for Diesel Engine Service (Obsolete)

Service typical of certain naturally aspirated, turbocharged or supercharged diesel engines where highly effective control of wear and deposits is vital or when using fuels of a wide quality range, including high-sulfur fuels. Oils designed for this service were introduced in 1955 and provide protection from high-temperature deposits in these diesel engines.
 

Engine Test Requirements: 1-G2, L-38.


CC for Diesel Engine Service (Obsolete)

Service typical of certain naturally aspirated and lightly supercharged diesel engines operated in moderate to severe service, and certain heavy-duty gasoline engines. Oils designed for these service provided protection from high-temperature deposits and bearing corrosion in these diesel engines and from rust, corrosion and low-temperature deposits in gasoline engines. These oils were introduced in 1961.
 

Engine Test Requirements: L-38, LTD or Modified LTD; IIC or IID; 1-H2.
 

CB for Diesel Engine Service (Obsolete)

Service typically of diesel engines operated in mild to moderate duty. Oils designed for this service provided necessary protection from bearing corrosion and high-temperature deposits in normally-aspirated diesel engines with lower quality fuels. Oils of API Service Category CB should not be used in any engine unless specifically recommended by the manufacturer.
 

Engine Test Requirements: L4 or L-38, L-1.
 

CA for Diesel Engine Service (Obsolete)

Service typical of diesel engines operated in mild to moderate duty with high-quality fuel. Oils designed for this service provided protection from bearing corrosion and from ring belt deposits in some naturally aspirated diesel engines when using such quality fuels that they imposed no unusual requirements for wear and deposit protection. Oils of API Service Category CA should not be used in any engine unless specifically recommended by the manufacturer.

Engine Test Requirements: L-4 or L-38, L-1. 
 

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