API stands for American Petroleum Institute. In 1970, along with the SAE and ASTM (American Society for Testing and Materials), they established the API Service Classification System to define the performance level of a given oil, unrelated in the main, to oil viscosity.
The API requirements “S” for Spark Ignition (petrol) and “C” for Compression Ignition (diesel) can be briefly described as follows. The latest API “S” and “C” classifications are backwards compatible and suitable for use in place of earlier classifications. (Note we have omitted obsolete designations for brevity).
Petrol
SJ - Meets 1998-2000 requirements of Automotive manufacturers. SL – Meets 2001-2004 requirements of Automotive manufacturers. SM – Meets 2004-2010 requirements of automotive manufacturers. XW-20 and XW-30 grades have chemical limits.
SN – Introduced in October 2010, designed to provide improved high temperature deposit protection for pistons, more stringent sludge control and seal compatibility. API SN with Resource Conserving matches ILSAC GF-5 by combining API SN performance with improved fuel economy, turbo charger protection, emission control system compatibility and protection of engines using E85 fuel.
SN Plus – Licensed from May 2018 as a supplement to API SN and ILSAC GF-5 to ensure that engine oils properly protect against low speed pre-ignition (LSPI), a severe engine performance issue that affects gasoline direct injected (GDI) and turbocharged GDI (T-GDI) engines.
SP – Introduced from May 2020, with added performance benefits required to meet the demands of modern engine technology – including, engine downsizing, gasoline direct injection (GDI), turbocharging and gasoline particulate filters (GPFs). Engine oils meeting the requirements of API SP deliver several performance advantages versus current API SN and API SN PLUS categories for spark- ignited internal combustion engines.
Diesel
CH-4 – Introduced in 1998 for high speed four stroke diesel engines meeting 1998 emission standards (less than 0.5 percent sulphur). Can replace API CD, CE, CF-4 & CG-4 oils.
CI-4 – Introduced in September 2002 for high speed four stroke diesel engines, designed to meet 2004 exhaust emission standards and using low sulphur fuel (less than 0.5 percent). Can replace API CD, CE, CF-4, CG-4 & CH-4 oils.
CI-4 – As per CI-4 but with further restrictions on PLUS after shear viscosity and performance.
CJ-4 – Introduced in 2006 for 15ppm maximum fuel sulphur. Enhanced wear protection, 1.0 percent ash maximum. For engines designed to meet 2010 model year on-highway emission standards. Effective where particulate filters and other after- treatment systems are used. Improved performance for soot handling, oxidative thickening, engine wear piston deposit formation, foaming and viscosity loss due to shear. Can replace API CI-4 Plus, CI-4, CH-4, CG-4 & CF-4 oils.
Starting from December 1st 2016, the API (American Petroleum Institute) launched two new diesel specifications with the aim of providing enhanced engine protection, lower fuel economy and to help meet new US environmental regulations starting in 2017. Both specifications are designed to provide enhanced engine protection for heavy duty engines.
CK-4 effectively replaces API CJ-4 and is backward compatible with most applications where currently an API CJ-4, CI-4/Plus or CH-4 oil is recommended.
CK-4 oils are designed for use in high-speed four-stroke diesel engines that are designed to meet 2017 model year, on- highway and Tier 4 non-road exhaust emission standards (reduction of particle matter and NOx) as well as being compliant for previous model year diesel engines.
These oils are effective at sustaining emission control system durability where particulate filters and other advanced after treatment systems are used. API CK-4 oils are designed to provide enhanced protection against oil oxidation, viscosity loss due to shear and oil aeration as well as protection against catalyst poisoning, particulate filter blocking, engine wear, piston deposits, degradation of low- and high-temperature properties and soot-related viscosity increase.
Note: When using CK-4 oil with higher than 15 ppm sulphur fuel, consult the engine manufacturer for service interval recommendations.
These oils are formulated for use in all applications with diesel fuels ranging in sulphur content up to 500 ppm (0.05 percent by weight). However, the use of these oils with greater than 15 ppm (0.0015 percent by weight) sulphur fuel may impact exhaust after-treatment system durability and/or oil drain interval.
FA-4
API FA-4 oils are XW-30 oils specifically formulated for use in select high-speed four-stroke diesel engines designed to meet 2017 model year on-highway greenhouse gas (GHG) emission standards. FA-4 oils provide similar improvements to CK-4 oils but they are NOT backward compatible with earlier engines. These oils are designed for use in on-highway engines manufactured from 2017 onwards. This specification requires a XW-30 viscosity grade oil with a low HTHS viscosity (between 2.9 cP and 3.2 cP). FA-4 oils are NOT interchangeable or backward compatible with API CK-4, CJ-4, CI-4, CI-4PLUS and CH-4 oils. Users need to refer to engine manufacturer recommendations to determine if API FA-4 oils are suitable for use with their engine.
FA-4 oils are not recommended for use with fuels having greater than 15 ppm sulphur. For fuels with sulphur content greater than 15 ppm, refer to engine manufacturer recommendations. These oils are formulated for use in on-highway applications with diesel fuel sulphur content up to 15 ppm (0.0015 percent by weight).
These oils are blended to a high temperature high shear (HTHS) viscosity range of 2.9cP–3.2cP to assist in reducing GHG (Green House Gas) emissions. They are effective at sustaining emission control system durability where particulate filters and other advanced after-treatment systems are used.
