Should API CK-4 Engine Oil Be Used In Older Diesel Engines?
A reader asks: I’ve got a 2003 Dodge Ram 2500 with the 5.9L Cummins engine. Should I use the older generation of CI-4+ diesel oils? Are the newer API CK-4 diesel oils good for this engine? My understanding is that these engines have flat tappet cams and I hear that the newer diesel oils do…



