API Launches New Diesel Oil Service Symbols: CL-4 and FB-4

The American Petroleum Institute (API) announced that the new API Proposed Category 12 (PC-12) heavy-duty engine oil specification has been formally approved and will be incorporated into API 1509, the Engine Oil Licensing and Certification System (EOLCS) document.

With this milestone, the API Service Category CL-4 and API FB-4 “Donut” certification marks are now available. Oil marketers can begin finalizing formulations and preparing product packaging to meet the new specifications ahead of the first licensing date of January 1, 2027.

“To support the next generation of heavy-duty engine technology and emissions standards, PC-12 establishes a strong technical foundation for performance, durability and environmental protection,” said Bill O’Ryan, Director-EOLCS/DEF with API. “Making the CL-4 and FB-4 service symbols available now allows oil marketers to prepare for a smooth transition as we approach the 2027 model year.”

To further support industry readiness, the API licensee portal will open on June 1, 2026. This early-access period will allow licensees to proactively enter new API CL-4 and API FB-4 products into the system.

The new engine oil specifications are designed to prepare the heavy-duty engine oil marketplace for next-generation performance standards, including improved oxidation resistance, enhanced wear protection, expanded elastomer compatibility, improved aftertreatment system protection and support for lower viscosity grades aimed at improving fuel economy.

API1509
API 1509, Engine Oil Licensing and Certification System, describes the voluntary API EOLCS program, the process for developing new engine oil performance standards and the requirements for licensing and proper use of the API Marks. The document also outlines aftermarket audit and enforcement procedures to help ensure that products licensed as meeting API standards continue to satisfy those requirements in the marketplace.

For more information about PC-12 and API’s Engine Oil Licensing and Certification System, visit API.org/EOLCS.