Ask the Expert: What is the difference between CK-4 and FA-4?

May 18, 2016
The primary difference in the two new API performance categories for heavy duty oil is with backward compatibility.

Q: What is the difference between CK-4 and FA-4?

A: The primary difference in the two new API performance categories for heavy duty oil is with backward compatibility. API CK-4 oils will be recommended for virtually all high-speed four stroke cycle diesel engines – including older engines that were using API CJ-4, as well as new engines that are currently being developed. The use of API FA-4 oils will be more limited and OEMs will not recommend them for use in most older diesel engines. This API FA-4 category is focus on the next generation of on-highway diesel engines that were designed to take advantage of the fuel economy advantage of the thinner oil.

Other differences include:

  • API CK-4
    • Viscosity grades include both SAExW-40 and xW -30 engine oils with >3.5 cP high-temperature high-shear (HTHS) viscosity
    • Higher level of wear and oxidation protection compared API CJ-4 oils
    • Improved shear stability
  • API FA-4
    • The same wear and oxidation protection required for API CK-4
    • Improved fuel economy
    • Applies only to SAE 10W-30 and SAE 5W-30 viscosity grades that have HTHS viscosity in the range of 2.9 to 3.2 cP
    • Developed to protect engine parts even with thinner oil films

Information provided by: Chevron

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