API approved two new diesel oil standards, FA-4 and CK-4, earlier this year.
“API is introducing a diesel engine oil category for use in truck engines designed to meet 2017 model year on-highway greenhouse gas emission standards,” said Kevin Ferrick, senior manager for engine oil licensing. “The FA-4 donut was developed to help truck owners who need FA-4 oils easily recognize the oil and distinguish it from CK-4 oils.”
The new donut features a shaded section to differentiate API FA-4 diesel oils from CK-4 oils. The API CK-4 Service Symbol Donut will look the same as the current CJ-4 Donut.
API has put together this website with more information on FA-4 and CK-4 engine oils.