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API Engine Oil Classifications

The American Petroleum Institute (API) has established a classification system for the designation of gasoline and diesel engine oils which reflects the oils quality, performance and suitability for various engines. These classifications, or categories as sometimes referred, have no bearing on oil viscosity, whose limits are set by the Society of Automotive Engineers (SAE) and designated in SAE J300. Contrary to the belief of many, SAE grade only defines the oil’s viscosity and has absolutely nothing to do with oil quality. To specify an engine oil, both the API service designation and the SAE viscosity grade are required.

In the United States, the API also administers the licensing and certification of engine oils through a classification system that reflects the warranty, maintenance and lubrication requirements of the automotive industry. Through this system, API has
standardized the –labeling of engine oils by adopting the “donut logo”, which tells the user the oil’s viscosity grade, engine service classification and any energy conserving capabilities. Engine oil performance requirements, test methods and limits for the various classifications are established by the engine and vehicle manufacturers and technical societies.

These classifications are arranged into two different groups, one for automotive gasoline engine service and one for commercial diesel engine service. The former is listed in “S”, or “service” oils (presently SA through SH) and the later is listed in “C”, or “commercial” oil (presently CA through CG-4) classifications. The higher the second letter, alphabetically, in the designation, the higher quality and performance offered by that oil.

SA – Utility Gasoline and Gasoline Engine Service (Obsolete)

This category denotes service typical of older engines operated under such mild conditions that the protection afforded by compounded oils is not required. This classification has no performance requirements, and oils in this category should not be used in any engines unless specifically recommended by the engine manufacturer.

SB – Minimum Gasoline Engine Service (Obsolete)

This category denotes service typical of older engines operated under such mild conditions that only minimum protection afforded by compounding is desired. Oils designed for this service have been used since the 1930s and provide only mild antis cuff capability and resistance to oxidation and bearing corrosion. They should not be used in any engines unless specifically recommended by the engine manufacturer.

SC – 1964 Gasoline Engine Warranty Maintenance Service (Obsolete)

This category denotes service typical of gasoline engines in 1964 through 1967 models of passenger cars and some trucks, operating under engine manufacturers’ warranties in effect during those model years. Oils designed for this service provide control of high and low temperature deposits, wear, rust and corrosion in gasoline engines.

SD – 1968 Gasoline Engine Warranty Maintenance Service (Obsolete)

This category denotes service typical of gasoline engines in 1968 through 1970 models of passenger cars and some trucks, operating under engine manufacturers’ warranties in effect during those model years. This category may also apply to certain 1971 or later models as specified (or recommended) in the owners’ manuals. Oils designed for this service provide more protection against high and low-temperature deposits, wear, rust and corrosion in gasoline for API Service Category SC and may be used when API Engine Service Category SC is recommended.

SE – 1972 Gasoline Engine Warranty Maintenance Service (Obsolete)

This category denotes service typical of gasoline engines in passenger cars and some trucks beginning 1972 and certain 1971 through 1979 models operating under engine manufacturers’ warranties. Oils designed for this service provide more protection against oil oxidation, high-temperature engine deposits, rust and corrosion in gasoline engines than oils that are satisfactory for API Engine Categories SD or SC and may be used when either of these categories is recommended.

SF – 1980 Gasoline Engine Warranty Maintenance Service (Obsolete)

This category denotes service typical of gasoline engines in passenger cars and some trucks beginning with 1980 through 1989 models operating under engine manufacturers’ recommended maintenance procedures. Oils developed for this service provide increased oxidation stability and improved anti-wear performance relative to oils that meet the minimum requirements of API Service Category SE. These oils also provide protection against engine deposits, rust and corrosion. Oils meeting API Service Category SF may be used when API Engine Service Categories
SE, SD, or SC are recommended.

SG – 1989 Gasoline Engine Warranty Maintenance Service (Obsolete)

This category denotes service typical of gasoline engines in present passenger cars, vans and light trucks operating under manufacturers’ recommended maintenance procedures. Category SG oils include the performance properties of API Service Category CC, (Certain manufacturers of gasoline engines require oils that also meet the higher diesel engine Category CD.) Oils developed for this service provide improved control of engine deposits, oil oxidation, and developed for previous categories. These oils also provide protection against rust and corrosion. Oils meeting API Service Categories SF, SE, SF/CC, or SE/CC are recommended.

SH – 1994 Gasoline Engine Warranty Maintenance Service (Obsolete)

This category was adopted in 1992 to describe engine oil first mandated in 1993. It is for use in service typical of cars, vans and light trucks operating under vehicle manufacturers’ recommended maintenance procedures. Engine oils developed for this category provide performance exceeding the minimum requirements of API Service Category SG, which it is intended to replace, in the areas of deposit control, oil oxidation, wear, rust, and corrosion. Oils meeting API SH requirements have been tested according to the Chemical Manufacturers Association (CMA) Product Approval Code of Practice and may utilize the API Base Oil Interchange and Viscosity Grade Engine Testing Guidelines. They may be used where API Service Category SG and earlier categories are recommended.

SJ – 1997 Gasoline Engine Warranty Maintenance Service

This category was adopted in 1996 to describe engine oil first mandated in 1997. It is for use in service typical of gasoline engines  passenger cars, vans, and light trucks operating under vehicle manufacturers’ recommended maintenance procedures. Oils meeting API SJ requirements have been tested according to the American Chemistry Council (ACC) product Approval Code of Practice and may utilize the API Base Oil Interchange and Viscosity Grade Engine Testing Guidelines. They may be used where API Service Category SH and earlier
categories are recommended.

SL – 2001 Gasoline Engine Warranty Maintenance Service

This is  engine category specification was introduced in July 1, 2001. It is for use in service typical of gasoline engines in passenger cars, sport utility vehicles, vans and light trucks operating under vehicle manufacturers’ recommended maintenance procedures. Oils meeting API SL requirements have been tested according to the American Chemistry Council (ACC) Product Approval Code of Practice and may be utilize the Base Oil interchange and Viscosity Grade Engine Testing Guidelines. They may be used where API Service Category SJ and earlier categories are recommended. SL oils are designed to provide better high-temperature deposit control and lower oil consumption.

SM – 2004 Gasoline Engine Warranty Maintenance Service

This category specification was intoruduced in 2004 for use in service typical of gasoline engines beginning for the 2010 and older passenger cars, sport utility vehicles, vans and light trucks operating under vehicle manufacturers’ recommended maintenance procedures. SM oils are being designed to provide better oxidative control, deposit protection and improved fuel economy performance along with further reduction in sulfur and phosphorous levels. Some of these grades may also meet the latest ILSAC specification and/or qualify as Energy Conserving.

SN – 2010 Gasoline Engine Warranty Maintenance Service (Current)

This is the most current category specification  intoruduced in 2010 for use in service typical of gasoline engines for passenger cars, sport utility vehicles, vans and light trucks operating under vehicle manufacturers’ recommended maintenance procedures. SN oils are being designed to provide improved high temperature deposit protection for pistons, more stringent sludge control, and seal compatibility. Some of these grades may also meet the latest ILSAC GF-5 specification and/or qualify as Resource Conserving combining API SN performance with improved fuel economy, turbocharger protection, emission control system compatibility, and protection of engines operating on ethanol-containing fuels up to E85.

CA – Diesel Engine Service (Obsolete)

This category denotes service typical of diesel engines operated in mild to moderate duty with high-quality fuels; occasionally has included gasoline engines in mild service. Oils designed for this service provide protection from bearing corrosion and ring-belt deposits in some naturally aspirated diesel engines when using fuels of such quality that they impose no unusual requirements for wear and deposit protection. They were widely used in the 1940s and 1950s but should not be used in any engine unless specifically recommended by the equipment manufacturer.

CB – Light Duty Diesel Engine Service (Obsolete)

This category denotes service typical of diesel engines operated in mild to moderate duty, but with lower quality fuels, which necessitate more protection from wear and deposits; occasionally has included gasoline engines in mild service. Oils designed for this service were introduced in 1949. They provide necessary protection from bearing corrosion and from high-temperature deposits in naturally aspirated diesel engines with higher sulfur fuels.

CC – Moderate Duty Diesel Engine Service (Obsolete)

This category denotes service typical of certain naturally aspirated, turbo-charged or supercharged diesel engine operated in moderate to severe-duty service, and certain heavy-duty gasoline engines. Oils designed for this service provide protection from high-temperature deposits and bearing corrosion in these diesel engines, and
also from rust, corrosion, and low-temperature deposits in gasoline engines. These oils were introduced in 1961.

CD – Severe Duty Diesel Engine Service (Obsolete)

This category denotes service typical of certain naturally aspirated, turbo-charged or supercharged diesel engines where highly effective control of wear and deposits is vital, or when using fuels with a wide quality range (including high-sulfur fuels). Oils designed for this service were introduced in 1955 and provide protection from high-
temperature deposits and bearing corrosion in these diesel engines.

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

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

CE – 1983 Severe Duty Diesel Engine Service 

(Obsolete)

This category denotes service typical of certain turbo-charged or supercharged heavy-duty diesel engines, manufactured since 1983 and operated under both low-speed, high-load and high-speed, high-load conditions. Oils designated for this service may also be used when API Service Category CD is recommended for diesel engines.

CF – For Off-Road Indirect Injected Diesel Engine Service (Obsolete)

This category denotes service typical of off-road indirect injected (pre-chamber) diesel engines and other diesel engines that use a broad range of fuel types including those using fuel with higher sulfur content, for example, over 0.5% wt.

CF-2 – Severe Duty Two-Stroke Cycle Diesel Engine Service 

(Obsolete)

This category denotes service typical of two-stroke cycle diesel engines requiring highly effective control of wear and deposits. Oils designed for this service demonstrate improved performance over API CD-II oils and can be used wherever API Service Category CD-II oils are recommended.

CF-4 – 1990 Severe Duty Four-Stroke Cycle Diesel Engine Service 

(Obsolete)

This category denotes service typical of high-speed, four-stroke cycle diesel engines. API CF-4 oils exceed the requirements for the API CE category, providing improved control of oil consumption and piston deposits. These oils should be used in place of API CE oils. They are particularly suited for on-highway, heavy- duty truck applications. When combined with the appropriate “S” category, they can also be used in gasoline and diesel powered personal vehicles — i.e., passenger cars, light trucks, and vans — when recommended by the vehicle or engine manufacturer.

CG-4 – 1994 Diesel Engine Service 

(Obsolete)

This category denotes service typical of high speed four-stroke cycle diesel engines used in both heavy duty on-highway (0.05% wt. sulfur fuel) and off-highway (less than 0.5% wt. 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 exhaust emission standards and may also be used in engines requiring API Service Categories CD, CE and CF-4. Oils designated for this service have been in existence since 1994.

CH-4 – 1998 Diesel Engine Service

These oils are suitable for high-speed four-stroke diesel engines designed to meet 1998 exhaust emission standards, and are specifically compounded for use with diesel fuels ranging in sulfur content up to 0.5% weight. CH-4 oils exceed the performance of API service CF-4 and CG-4 oils, and can effectively lubricate engines
calling for those API service categories. These oils were introduced in December 1998.

CI-4 – 2002 Diesel Engine Service

The CI-4 performance requirements describe oils for use in those high-speed, four-stroke cycle diesel engines designed to meet 2004 exhaust emission standards,implemented October 2002. These oils are compounded for use in all applications with diesel fuels ranging in sulfur content up to 0.5% by weight. These oils are especially effective at sustaining engine durability where Exhaust Gas Recirculation (EGR) and other exhaust emission componentry may be used. Optimum protection is provided for control of corrosive wear tendencies, low and high temperature stability, soot handling properties, piston deposit control, valve train wear, oxidative thickening, foaming and viscosity loss due to shear. CI-4 oils are superior in performance to those meeting API CH-4, CG-4 and CF-4 can effectively lubricate engines for those API Service Categories. Meets Detroit Diesel specifications DDC 93K214.

CI-4 Plus – 2004 Diesel Engine Service

The CI-4 Plus performance requirements implemented in September 2004, were designed to address the concerns of industry regarding high soot loading and viscosity increases problems received by OEM on a limited number of engines in field service. These oils are especially effective at sustaining engine durability where Exhaust Gas, Recirculation (EGR), and other exhaust emission componentry with enhancements to the soot and viscosity control along with additional engine testing over and above the original CI-4 formulations. CI-4 Plus oils are superior in performance to those meeting API CI-4, CH-4, CG-4 and CF-4 can effectively lubricate engines for those API Service Categories.

CJ-4 – 207 Diesel Engine Service

 (Current)
The CJ-4 performance requirements for high-speed four stroke cycle diesel engines designed to meet 2010 model year on-highway and Tier 4 nonroad exhaust emission standards as well as for previous model year diesel engines. These oils are formulated for use in all applications with diesel fuels ranging in sulfur content up to 500 ppm (0.05% by weight). However, the use of these oils with greater than 15 ppm (0.0015% by weight) sulfur fuel may impact exhaust after treatment system durability and/or drain interval. CJ-4 oils are especially effective at sustaining emission control system durability where particulate filters and other advanced after treatment systems are used. Optimum protection is provided for control of catalyst poisoning, particulate filter blocking, engine wear, piston deposits, low- and high-temperature stability, soot handling properties, oxidative thickening, foaming, and viscosity loss due to shear. API CJ-4 oils exceed the performance criteria of API CI-4 with CI-4 PLUS, CI-4, CH-4, CG-4 and CF-4 and can effectively lubricate engines calling for those API Service Categories.

When using CJ-4 oil with higher than 15 ppm sulfur fuel, consult the engine manufacturer for service interval.

Automotive Gear Lubricant Classifications

Automotive gear lubricants, similar to engine oils, are classified by the API in terms of quality depending on the performance required by a particular application. As in the case of engine oils, these classifications do not define or reflect oil viscosity. To completely specify a gear lubricant, both the API service designation and the SAE
viscosity grade are required.

Axle and transmission lubricant viscosities are defined separately in SAE J306 recommended practice. Multi-grade lubricants are normally used and each viscosity grade has distinct criteria for low and high-temperature performance.

API GL-5 quality gear lubricants possess adequate extreme pressure characteristics for essentially all automotive gear applications to prevent wear, pitting, scoring and ultimate gear failure, along with protection against oxidation, thermal degradation, rust, copper corrosion, foaming and water emulsification. API GL-5 oils are relatively equivalent to MIL-L-2105D gear lubricants and are the most widely used automotive gear lubricants in North America for automobile, truck, bus and heavy construction equipment applications.

Due to changes in manufacturers’ recommended practices or due to the unavailability of proper testing hardware, the Service Designations API GL-2, GL-3 and GL-6 are no longer in current use.

Service Designations in Current Use

GL-1

This designation denotes lubricants intended for manual transmissions operating under such mild conditions that straight petroleum or refined petroleum oil may be used satisfactorily. Oxidation and rust inhibitors, defoamers and pour depressants may be added to improve the characteristics of these lubricants. Frictional modifiers and extreme pressure additives shall not be used. Untreated oil is generally not a satisfactory lubricant for many passenger car manual transmissions because of the operating speeds and loads involved. However, untreated oils may be used successfully in some truck and tractor manual transmissions. In all cases the transmission manufacturer’s lubricant quality recommendations should be followed.

GL-4

This designation denotes lubricants intended for axles with spiral bevel gears operating under moderate to severe conditions of speed and load or axles with hypoid gears operating under moderate speeds and loads. These oils may be used in selected manual transmission and transaxle applications. The manufacturer’s specific lubricant quality recommendations should be followed. Although this service designation is still used commercially to describe lubricants, some test equipment used for performance verification is no longer available. Procedures to define this
performance are currently being reviewed for adoption by ASTM.

GL-5

This designation denotes lubricants intended for gears, particularly hypoid gears, in axles operating under various combinations of high-speed, low-speed, high-torque, and shock-load conditions. Lubricants qualified under U.S. Military Specification MIL- PRF-2105E (formerly MIL-L-2105D) satisfy the requirements of the API-GL-5 service designation. Performance test details are in ASTM Publication STP-512A, “Laboratory Performance Tests for Automotive Gear Lubricants intended for API-GL-5 Service.

Service Designations Not in Current Use

GL-2

This designation denotes lubricants intended for automotive worm-gear axles operating under such conditions of load, temperature, and sliding velocities that lubricants satisfactory for API-GL-1 service will not suffice. Products suited for this type of service contain anti-wear or film-strength improvers specifically designed
to protect worm gears.

GL-3

This designation denotes lubricants intended for manual transmissions operating under moderate to severe conditions and spiral-bevel axles operating under mild to moderate conditions of speed and load. These service conditions require a lubricant having load-carrying capacities exceeding those satisfying API-GL-1 service but below the requirements of lubricants satisfying API-GL-4 service. Gear lubricants designated for API-GL-3 service are not intended for axles with hypoid gears. Some transmission and axle manufacturers specify API Category “CC” or “CD” motor oils for this service. The manufacturer’s specific lubricant quality
recommendations should be followed.

GL-6

This designation denotes lubricants intended for gears designed with a very high pinion offset. Such designs typically require protection from gear scoring in excess of that provided by API-GL-5 gear oils. A shift to more modest pinion offsets and the obsolescence of original API-GL-6 test equipment and procedures have greatly
reduced the commercial use of API-GL-6 gear lubricants.