API’s Engine Oil Licensing and Certification System (EOLCS) is a licensing and certification program that authorizes engine oil marketers that 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 Fiat Chrysler and those represented by the Japan Automobile Manufacturers Association and the Truck and Engine Manufacturers Association. The performance requirements and test methods are established by vehicle and engine manufacturers and technical societies and trade associations such as (ASTM), (SAE), and the American Chemistry Council (ACC).

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The Engine Oil Program is backed by a 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.