For fleet operators, every maintenance decision connects to a larger goal: keeping equipment working reliably while managing operating costs. As engine technology evolves, lubricant selection remains an important part of that equation.

The next generation of heavy duty diesel engine oil categories, API CL-4 and FB-4, developed through PC-12, reflects changing demands for engine and emissions-system protection. With first licensing beginning January 1, 2027, you have an opportunity to help customers understand the changes and help them plan ahead.

Two Categories. Different Equipment Needs.

CL-4 and FB-4 take different approaches to meeting the needs of evolving fleets. CL-4 succeeds CK-4 and is designed to be backward compatible with engines that currently require CK-4 oils, providing a path forward for both existing equipment and newer engines. FB-4 succeeds FA-4, supporting lower-viscosity formulations for engines specifically designed and approved to use them. Both categories strengthen performance requirements for oxidation control and wear protection.

Early conversations with a lubricant supplier can help identify those needs before products enter the shop. January 1 marks the start of licensing, rather than a requirement for every fleet to switch immediately. For your business, these conversations create an opportunity to strengthen customer relationships through informed guidance. Asking the right questions today can help customers make confident decisions as their fleets evolve.

Visit the Phillips 66^® Lubricants PC-12 resource page for more information, frequently asked questions and a downloadable CL-4 and FB-4 Educational Guide to support your customer conversations.