Today’s engine oils are marvels of fluid engineering, delivering robust protection for modern, high-performance engine technology across both passenger cars and heavy-duty diesel trucks. In many ways, they are the lynchpin of modern transportation and key enablers of the best of what today’s engine technology has to offer.

Across both the passenger car and heavy-duty sectors, engine oils’ evolution has largely been driven by performance specifications, which are developed and issued in response to changing hardware requirements.

The industry is now developing the next passenger car engine oil performance category, ILSAC GF-8, which is currently targeting first licensing in Q3 2028, while the heavy-duty industry is preparing for the first licensing of API CL-4 and API FB-4 on January 1, 2027. These changes will significantly affect how engine oils are formulated and marketed, while elevating performance across each industry.

In anticipation of these changes, it’s worth asking: What’s in a spec?

Much goes into the development and issuance of a new specification, and understanding this process helps oil marketers remain prepared for changes. Let’s take a closer look at the steps involved:

Step 1: New Regulatory Measures are Introduced

New specifications in the passenger car and heavy-duty diesel markets are initially driven by the implementation of new regulatory measures that set elevated requirements for new model vehicles.

Typically, these include new limitations on emissions and prioritize greater fuel economy; OEMs must in turn develop new hardware to satisfy the requirements.

Step 2: Request for Specification

Because meeting such requirements involves contribution from the engine oil, a consortium of OEMs will then issue a request for a new specification to be developed.

For example, heavy-duty diesel OEMs are represented by the Truck & Engine Manufacturers Association (EMA). Prior to the development of API CL-4 and API FB-4, the EMA issued a formal needs statement, outlining their desired performance improvements from the current generation of heavy-duty diesel engine oils (licensed under API CK-4 and API FA-4). ILSAC specifications follow the same general process.

Step 3: Early Development

Representatives from the engine oil industry form a new category development team (NCAT) to determine whether the changes requested in the needs statement merit the full development and investment in a new category.

This group involves:

Members of the American Chemistry Council (ACC), representing additive companies.
Members of the American Petroleum Institute (API), representing major oil marketers.

It’s not uncommon for some back and forth between the NCAT and the EMA in settling upon broad requirements of a new category. Once settled, the process moves onto the next step.

Step 4: Testing Matrix Evaluation and Development

To satisfy the finalized needs statement, category developers must then determine the appropriate testing matrix to evaluate new engine oils’ ability to deliver the required performance. First, developers typically look to the previous performance category’s test matrix:

In some cases, previous-generation tests are run on aging engines no longer in development and must be retired and replaced.
In other cases, entirely new tests must be developed to satisfy new performance requirements.

For example, PC-12 development for API CL-4 and API FB-4 has included key updates to the testing matrix, such as the addition of the Detroit Diesel DD13 scuffing test and the planned use of a Cummins ISB-based procedure to address soot-related viscosity control.

The Cummins ISB-V test for soot related viscosity increases
The Detroit Diesel 13 scuffing test for piston and liner scuffing or adhesive wear.

ILSAC GF-8 is also expected to include updated testing to support fuel economy and modern engine operating conditions.

What’s in a Spec? ILSAC GF-8, API CL-4, and Beyond