API 1509, Engine Oil Licensing and Certification System, 18th Edition
The latest standards and marketing guidelines for API Engine Oil Quality Marks governs how engine oil marketers certify that gasoline and diesel engine oils meet API’s stringent performance standards.
API 1509 describes the voluntary API Engine Oil Licensing and Certification System (EOLCS) as well as methods for developing new engine oil performance standards. It also provides sellers with a description of the API Marks and their use, licensing requirements, and aftermarket conformance and enforcement procedures that help to ensure that products licensed as or claiming to meet API standards actually do meet the standards.
The 18th version of API 1509 is now available here.