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

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