The Ram 3500 diesel, typically powered by the Cummins 6.7L engine, most often uses a full-synthetic diesel oil with a viscosity of 5W-40 that meets API CK-4 or FA-4 specifications. Always confirm the exact requirements for your year and engine in the owner's manual or on the oil fill cap.
Diesel engines in heavy-duty Ram trucks face high temperatures and heavy loads, especially when towing or working hard. Over time, emissions controls and engine design have evolved, which has influenced the oil specification and viscosity recommended for different model years. Because these requirements can vary by year, region, and engine variant, checking official guidance is essential.
Key oil specifications for the Ram 3500 diesel
Here is a concise guide to the most common, up-to-date oil specifications for most 6.7L Cummins Ram 3500 diesels. Use this as a starting point, then confirm with your owner's manual.
- Full-synthetic diesel engine oil — designed for turbocharged diesel engines and high-load operation.
- Viscosity: 5W-40 — the most common choice across modern 6.7L Cummins engines in Ram trucks.
- API service requirement: CK-4 or FA-4 — these are the standard API classifications for newer diesel engines with emissions controls. CK-4 is widely accepted; FA-4 is often allowed for certain engines and climates.
- OEM compatibility: Look for oils that meet or exceed the OEM specification; many Ram/Mopar-approved oils are marketed to meet these specs.
Note: If you have an older Ram 3500 with a pre-emissions or older Cummins configuration, the recommended oil could differ (some older 6.7L variants or other engine options may tolerate 15W-40). Always consult the owner's manual or a dealer for the exact specification for your exact vehicle year, region, and usage.
Practical guidance and maintenance tips
Oil change intervals and climate considerations affect the recommended oil type and change frequency. In general, use a full-synthetic diesel oil that meets CK-4/FA-4 and a 5W-40 viscosity, and adhere to the oil change interval specified by the manufacturer, adjusting for severe service conditions such as towing, hot climates, or dusty environments.
For drivers who operate in extreme conditions or use biodiesel blends, verify compatibility with the oil you choose and follow the manufacturer’s guidance. If in doubt, consult a qualified technician or your local Ram dealer for a recommendation tailored to your vehicle’s year and usage.
Summary
In most Dodge Ram 3500 diesels equipped with the Cummins 6.7L engine, the standard oil is a full-synthetic diesel oil with a 5W-40 viscosity that meets API CK-4 or FA-4 specifications. Always verify your model year and emissions configuration in the owner's manual or with a dealer, as older engines or special editions may require different specifications.