API engine-oil service categories
This page summarizes API engine-oil service categories and related ILSAC passenger-car standards as of August 13, 2026. An oil may carry more than one performance claim. Always verify the required viscosity grade, API category, ILSAC standard, and any manufacturer-specific approval in the current vehicle or engine documentation.
For automotive gasoline engines, a newer API “S” category generally includes the performance of earlier gasoline categories. Diesel categories do not have the same universal backward-compatibility rule: use the engine manufacturer’s recommendation, particularly when considering API FA-4.
The letters SI, SK, and SO are omitted from the API gasoline-category sequence to avoid confusion with other systems.
ILSAC passenger-car gasoline-oil standards
ILSAC standards are closely related to API gasoline categories, but are not interchangeable names. API SQ with Resource Conserving corresponds to ILSAC GF-7A. GF-7B applies only to SAE 0W-16 oils.
| Standard | Status on August 13, 2026 | Summary |
|---|---|---|
| ILSAC GF-7A | Current | Introduced in March 2025. Adds protection against fresh- and aged-oil low-speed pre-ignition, timing-chain wear, deposits, sludge and varnish, while addressing fuel economy, emission-system protection, low-temperature pumpability, and engines using ethanol-containing fuel up to E85. See further details about ILSAC GF-7A. |
| ILSAC GF-7B | Current | Introduced in March 2025 for SAE 0W-16 oils only. It provides the GF-7 performance package for this very-low-viscosity grade. |
| ILSAC GF-6A | Current transition category | Introduced in May 2020. GF-7A is the replacement where GF-6A is specified. API identifies GF-6A as becoming obsolete on October 1, 2026. |
| ILSAC GF-6B | Current transition category | Introduced in May 2020 for SAE 0W-16 oils only. GF-7B is the replacement where GF-6B is specified. API identifies GF-6B as becoming obsolete on October 1, 2026. |
| ILSAC GF-5, GF-4, GF-3, GF-2, GF-1 | Obsolete | GF-7A is generally suitable where these earlier ILSAC standards are specified, subject to the vehicle manufacturer’s requirements. |
Gasoline engines: API “S” categories
| Category | Status on August 13, 2026 | Service and compatibility context |
|---|---|---|
| API SQ | Current | Introduced in March 2025. It addresses fresh- and aged-oil low-speed pre-ignition, timing-chain wear, high-temperature piston and turbocharger deposits, and sludge and varnish control. API SQ with Resource Conserving corresponds to ILSAC GF-7A and additionally includes fuel-economy, emission-system, low-temperature-pumpability, and E85-fuel protection requirements. See further details about API SQ. |
| API SP | Current | Introduced in May 2020. Designed for protection against low-speed pre-ignition, timing-chain wear, high-temperature piston and turbocharger deposits, sludge, and varnish. API lists it for 2025 and older automotive engines. API SP with Resource Conserving corresponds to ILSAC GF-6A. See further details about API SP. |
| API SN PLUS | Legacy interim classification | Licensed from May 1, 2018 as an LSPI-focused supplement used with API SN; it was not a separate API “S” service category. API SP subsequently became the newer gasoline category incorporating LSPI protection. For background, see what low-speed pre-ignition is and how it can be avoided. |
| API SN | Current | Introduced in October 2010 and listed by API for 2020 and older automotive engines. It improved high-temperature piston-deposit protection, sludge control, and seal compatibility. API SN with Resource Conserving corresponds to ILSAC GF-5. See further details about API SN. |
| API SM | Current | Introduced in 2004 and listed for 2010 and older automotive engines. It improved oxidation resistance, deposit control, wear protection, and low-temperature performance compared with earlier categories. |
| API SL | Current | Introduced for 2001 service and listed for 2004 and older automotive engines. |
| API SJ | Current | Introduced for 1997 service and listed for 2001 and older automotive engines. |
| API SH | Obsolete | Not suitable for most gasoline-powered automotive engines built after 1996; it may not provide adequate sludge, oxidation, or wear protection. |
| API SG | Obsolete | Not suitable for most gasoline-powered automotive engines built after 1993. |
| API SF | Obsolete | Not suitable for most gasoline-powered automotive engines built after 1988. |
| API SE | Obsolete | Not suitable for most gasoline-powered automotive engines built after 1979. |
| API SD | Obsolete | Not suitable for most gasoline-powered automotive engines built after 1971. |
| API SC | Obsolete | Not suitable for most gasoline-powered automotive engines built after 1967. |
| API SB | Obsolete | Not suitable for most gasoline-powered automotive engines built after 1951. Use only where specifically required for older equipment. |
| API SA | Obsolete | Contains no additive-performance requirement and is not suitable for most gasoline-powered automotive engines built after 1930. Use only where specifically required for older equipment. |
Diesel engines: API “F” category
| Category | Status on August 13, 2026 | Service and compatibility context |
|---|---|---|
| API FA-4 | Current | For certain SAE XW-30 oils intended for select high-speed, four-stroke on-highway diesel engines designed for 2017-model-year greenhouse-gas requirements. These oils have a high-temperature, high-shear viscosity of 2.9 to 3.2 mPa·s and are intended to help reduce greenhouse-gas emissions. FA-4 supports durability of advanced emission-control systems and addresses oxidation, shear-related viscosity loss, aeration, wear, deposits, low- and high-temperature properties, and soot-related viscosity increase. It is intended for on-highway diesel fuel containing up to 15 ppm sulfur. Important: API FA-4 is not interchangeable with, and is not backward compatible with, CK-4, CJ-4, CI-4 with CI-4 PLUS, CI-4, or CH-4. Use it only when the engine manufacturer permits FA-4. |
Diesel engines: API “C” categories
| Category | Status on August 13, 2026 | Service and compatibility context |
|---|---|---|
| API CK-4 | Current | For high-speed, four-stroke diesel engines designed for 2017-model-year on-highway and Tier 4 non-road emission requirements, as well as many earlier diesel engines. It is formulated for diesel fuels containing up to 500 ppm sulfur. CK-4 provides improved control of oxidation, shear-related viscosity loss, aeration, wear, deposits, low- and high-temperature properties, soot-related viscosity increase, catalyst poisoning, and particulate-filter blocking. It meets or exceeds the performance criteria of CJ-4, CI-4 with CI-4 PLUS, CI-4, and CH-4. Fuel above 15 ppm sulfur can affect aftertreatment durability and/or drain intervals; consult the engine manufacturer for the applicable service interval. |
| API CJ-4 | Current | For high-speed, four-stroke diesel engines designed for 2010-model-year on-highway and Tier 4 non-road emission requirements, as well as earlier engines. It is formulated for fuel containing up to 500 ppm sulfur and exceeds the performance criteria of CI-4 with CI-4 PLUS, CI-4, CH-4, CG-4, and CF-4. Fuel above 15 ppm sulfur can affect aftertreatment durability and/or drain intervals. |
| API CI-4 | Current | Introduced in 2002 for high-speed, four-stroke engines designed around 2004-emission requirements, including engines using exhaust-gas recirculation. It is intended for diesel fuel containing up to 0.5% sulfur and may be used where CD, CE, CF-4, CG-4, or CH-4 is specified. |
| API CI-4 PLUS | Supplemental classification | A designation used with qualifying CI-4 oils to indicate stronger control of soot-related viscosity increase and shear-related viscosity loss. It is not a separate API “C” service category. |
| API CH-4 | Current | Introduced in 1998 for high-speed, four-stroke diesel engines designed for 1998-emission requirements. It is intended for diesel fuel containing up to 0.5% sulfur and may be used where CD, CE, CF-4, or CG-4 is specified. |
| API CG-4 | Obsolete | Not suitable for most diesel-powered automotive engines built after 2009. |
| API CF-4 | Obsolete | Not suitable for most diesel-powered automotive engines built after 2009. |
| API CF-2 | Obsolete | Not suitable for most diesel-powered automotive engines built after 2009. Two-stroke diesel engines can have distinct lubricant needs; consult the engine manufacturer. |
| API CF | Obsolete | Not suitable for most diesel-powered automotive engines built after 2009. Some older equipment, particularly certain two-stroke or monograde applications, may still require this category. |
| API CE, CD-II, CD | Obsolete | Not suitable for most diesel-powered automotive engines built after 1994. |
| API CC | Obsolete | Not suitable for most diesel-powered engines built after 1990. |
| API CB | Obsolete | Not suitable for most diesel-powered engines built after 1961. |
| API CA | Obsolete | Not suitable for most diesel-powered engines built after 1959. Use only when specifically required by the equipment manufacturer. |
Reading API marks
API-licensed oil may display the API Service Symbol, commonly called the “Donut.” Gasoline oils show the applicable API “S” category; diesel oils show an API “C” or “F” category. A dual-rated diesel/gasoline oil may show both categories, but the presence of an API category does not replace an OEM-specific approval or the required SAE viscosity grade.