Home - engines - RAM Diesel Engines | Engine Oil Specifications RAM Diesel Engines | Engine Oil Specifications Home › Engines › RAM RAM Diesel Engines RAM diesel engines. Oil specifications, viscosity grades, and drain intervals for the 6.7L Cummins-powered RAM. Engine Pages 6.7L 6.7L Cummins CES 20081. 15W-40 or 5W-40. No FA-4. View spec → Cummins enginesCK-4 vs FA-4Best oil for semi trucks