The next-gen heavy-duty engine oil standard (PC-12) has been formally approved, announced the American Petroleum Institute, which also introduced the new CL-4 and FB-4 “donut” certification marks ahead of 2027 model-year engines.

This means 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.

The new engine oil specifications are designed to prepare the heavy-duty engine oil marketplace for next-generation performance standards.

The newest diesel engines need oils with:

• Improved oxidation resistance
• Enhanced wear protection
• Expanded elastomer compatibility
• Improved aftertreatment system protection
• Support for lower viscosity grades aimed at improving fuel economy.

Some of the improvements could benefit older engines as well.

For instance, improved oxidation stability, which helps engine oil resist breakdown at high temperatures, can help maintain oil quality over longer service intervals. That could help trucking fleets extend their oil drain intervals.

Additional wear-protection tests built into the category could also benefit older engines.

A Strong Technical Foundation

“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.

API's Oil Licensing and Certification Process

The new standard will be incorporated into API 1509, the Engine Oil Licensing and Certification System (EOLCS) document.

API 1509 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.