The 2018 Ram 6.7L Cummins diesel uses a synthetic diesel engine oil that meets API CK-4 or CJ-4 specifications and Cummins CES certification, with 5W-40 being the typical viscosity; always confirm exact requirements in your owner's manual for your vehicle and climate.
Oil specifications you should know
To ensure proper protection and compatibility, verify these standards on the oil you buy before pouring it into the engine.
- API CK-4 or CJ-4 diesel engine oil (not gasoline engine oil).
- Cummins engine oil certification (CES) for the 6.7L Cummins.
- Viscosity commonly recommended as 5W-40 synthetic diesel oil, suitable for a wide range of temperatures; follow the manual for any climate-specific guidance.
Choosing an oil that meets these specs helps protect the turbocharger, exhaust aftertreatment system, and overall engine performance.
Recommended oil brands and products
Below are widely available diesel oils that meet CK-4/CJ-4 and Cummins CES specifications. Always read the label to confirm the oil meets CK-4/CJ-4 and CES certification before purchasing.
- Mobil Delvac 1 ESP 5W-40
- Shell Rotella T6 5W-40
- Valvoline Premium Blue Diesel 5W-40
- AMSOIL Diesel Heavy Duty 5W-40
In practice, many owners and service centers rely on 5W-40 CK-4/CJ-4 oils from these brands; the key is ensuring the label clearly states CK-4 or CJ-4 and Cummins CES certification.
Maintenance tips and intervals
Always follow the oil-change interval recommended in your owner's manual, and consider more frequent changes under severe service, heavy towing, or extreme temperatures. Use the vehicle’s oil life monitor as a guide and verify that the recommended oil meets CK-4/CJ-4 and CES specifications.
Summary
For a 2018 Ram 6.7L Cummins, use a synthetic diesel oil that meets API CK-4 or CJ-4 and is Cummins CES-certified, with 5W-40 being the standard viscosity. Always consult your owner's manual and verify the oil label to ensure it meets the required specifications.