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About Engine Oil

API's Engine Oil Quality Marks—the API Service Symbol "Donut" and Certification Mark "Starburst"—help consumers identify quality engine oils for their gasoline- and diesel-powered vehicles.


API’s Engine Oil Licensing and Certification System (EOLCS) is a voluntary licensing and certification program that authorizes engine oil marketers who meet specified requirements to use the API Engine Oil Quality Marks. Launched in 1993, API’s Engine Oil Program is a cooperative effort between the oil and additive industries and vehicle and engine manufacturers Ford, General Motors, and Chrysler and those represented by the Japan Automobile Manufacturers Association and the Engine Manufacturers Association. The performance requirements and test methods are established by vehicle and engine manufacturers and technical societies and trade associations such as the American Society for Testing and Materials (ASTM), Society for Automotive Engineers (SAE), and American Chemistry Council (ACC).

The Engine Oil Program is backed by an ongoing monitoring and enforcement program that ensures licensees adhere to program requirements. This includes running physical, chemical, and performance tests on licensed engine oils and verifying that the API-registered Marks are properly displayed on containers and convey accurate information to consumers.

About half of the program’s more than 500 licensees are based in the United States, and the other half are spread among more than 50 countries. A complete list of licensees is available on our licensee directory. More than 8,000 products now display API Marks.


The program’s requirements are described in API 1509, Engine Oil Licensing and Certification System. This standard describes the program’s performance requirements, explains the current engine oil service categories, shows how the marks are to be used, and explains the monitoring and enforcement program. Standards referenced by API 1509, such as ASTM D 4485, Standard Specification for Performance of Engine Oils, and SAE J300, Engine Oil Viscosity Classification, also play a critical role in defining the program. These can be purchased through their sponsoring organizations.

Monitoring and Enforcement Program

API has been testing off-the-shelf engine oils carrying the API Starburst and Donut under its Aftermarket Audit Program (AMAP) since 1994 and in 1999 began testing product dispensed from tanks and drums at quick-lube facilities, service stations, auto dealerships, and truck maintenance facilities. AMAP superseded the Oil Labeling Assessment Program (OLAP), a testing program jointly funded by the U.S. Army, the Independent Lubricant Manufacturers Association (ILMA), the former American Automobile Manufacturers Association (AAMA), and API. In the last 10 years, API has tested more than 5,000 licensed oils from around the world.

Under AMAP, API-licensed engine oils are purchased in the marketplace and tested to determine their physical, chemical, and performance properties. The results are compared to licensee formulations on file at API. Conforming oils show test results that are consistent with the formulations on-file and meet program requirements. All samples undergo elemental analysis, viscosity at 100°C, and high-temperature/high-shear testing. They may also be tested for cold cranking, pumpability, volatility, gelation, foaming, filterability, flash point, and shear stability. Product packages are checked to make sure they correctly display the API Marks and carry product trace codes. A number of oils also undergo actual industry engine sequence testing for oxidation, deposits, sludge, varnish, and wear.


If a licensed oil does not match the physical and chemical data on file with API, API will work with the licensee to evaluate the nonconformity and take appropriate corrective action. Unresolved nonconformance issues are subject to additional enforcement actions spelled out in API 1509. Actions may include termination of the license to display the API Marks and removal of noncomplying product from the marketplace. If a licensed or unlicensed oil displays an improper label or unauthorized labeling data, API will require the marketer to cease and desist from committing the violation and will request verification that the violation has been corrected.