Nick King
Liberty, MO
CALL (816) 550-5556



Federal regulations are dictating that medium- and heavy-duty diesel vehicles must reduce fuel consumption and greenhouse gas emissions 15 percent by model year 2018, driving major changes in the diesel world. The API CJ-4 specification that has represented the standard for diesel oil performance for the past decade will soon give way to new specifications that will evolve with diesel technology to help ensure manufacturers meet federal mandates.


Two Specifications Replace CJ-4 Initially labeled Proposed Category 11 (PC-11) in its working stages, the new API specification has been split in two (API CK-4, FA-4) to accommodate the different requirements of older and newer engines. Both specs focus on drastically reducing emissions and improving fuel economy, while providing increased engine-protection benefits through improvements in oxidation stability, shear stability and resistance to aeration. Engine oils meeting the new specs will begin launching Dec. 1, 2016.


  • Offers traditional viscosity grades of 15W-40, 10W-30, 5W-40 and 5W-30
  • Designed for current model-year and older diesel engines
  • Backward-compatible with API CJ-4 (and prior) oils


  • Designed for certain 2017 and newer diesel engines
  • Not backward-compatible
  • Designed to improve fuel economy and reduce emissions
  • Primarily features 10W-30 viscosity grade

AMSOIL Prepared for Change 

AMSOIL Dealers can be wellassured that we will be ready for the implementation of the new diesel specifications with top-performing synthetic formulations. Details will be unveiled in upcoming issues of AMSOIL Magazine.

New Test Requirements 

In order to meet federal regulations, original equipment manufacturers (OEMs) are relying on engine designs that produce ever-increasing operating temperatures. The new API CK-4 and FA-4 specifications introduce new shear-stability requirements to minimize viscosity loss, as well as two new and updated tests to ensure additional protection benefits in the areas of oxidative stability and aeration resistance: 

New Mack T13 Test 

Measures oil oxidation under the higher temperatures common with modern engines.

New CAT Aeration Test 

Replaces the Engine Oil Aeration Test (EOAT), which used hardware that isn’t available anymore.

The rest of the tests carry over from API CJ-4.
We will get back to you as soon as we are able.


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