What kind of coolant does a 6.7 Cummins take?
The 6.7-liter Cummins diesel typically uses a long-life, ethylene glycol–based coolant that is phosphate-free and silicate-free, formulated for heavy‑duty diesel engines. Most owners run a 50/50 mix with distilled water unless the manufacturer specifies a different ratio.
Understanding the coolant requirements for the 6.7 Cummins
The 6.7L Cummins engine is designed to tolerate extended service intervals and aluminum components, so the coolant must protect against rust, corrosion, and scale without causing deposits. The right formulation is a long-life, ethylene glycol coolant that is explicitly labeled as suitable for Cummins engines or that meets Cummins’ internal CES specifications. Always verify with the owner’s manual or Cummins’ official guidance, as specs can vary by model year and application.
Key characteristics to look for in a coolant
- Ethylene glycol–based long-life formulation
- Phosphate-free and silicate-free (to prevent deposits and compatibility issues with aluminum)
- Explicitly labeled as Cummins-approved or meeting Cummins CES specifications
- Suitable for use in heavy‑duty diesel cooling systems and compatible with aluminum and cast iron components
- Contains appropriate corrosion inhibitors for diesel engines
Choosing a coolant that meets these criteria helps ensure proper protection of the cooling system and maintains warranty compliance. When in doubt, consult your manual or contact Cummins support for the latest CES specification referenced by your engine’s year and configuration.
Practical guidance for selecting and using the coolant
Before purchasing, inspect the label for compatibility with Cummins engines and the specified CES standard. Avoid using universal passenger car coolants unless they are explicitly rated for heavy‑duty diesel use and Cummins CES compliance. Many owners choose a high‑quality, OEM‑approved extended‑life coolant and follow the recommended service intervals in the manual. Store and mix coolant according to the product’s instructions and local water quality considerations.
Here are common options you may encounter while shopping for a 6.7 Cummins coolant.
- Long-life, heavy‑duty coolant labeled as Cummins-approved or meeting Cummins CES specifications
- Ethylene glycol–based formulations with phosphate- and silicate-free inhibitors
- Coolants certified for aluminum-heavy cooling systems and compatible with diesel engines
- Concentrates or pre-mixed 50/50 solutions, depending on your mix preference and climate
In summary, verify compatibility with Cummins CES standards and follow the manual for the exact specification and mix ratio. Using the wrong coolant can lead to corrosion, deposits, or cooling system failures.
Steps to change or flush the coolant
If you’re planning a coolant change, follow these general steps, noting that your vehicle’s service manual may specify a slightly different procedure:
- Park on a level surface and allow the engine to cool completely.
- Place a drain pan under the radiator drain plug and open the drain to remove the old coolant.
- Close the drain and fill with distilled water; run the engine to operating temperature to circulate the water, then drain again to flush the system.
- Close the drain, mix or fill with the proper 50/50 ethylene glycol–based coolant, and refill the reservoir to the correct level.
- Bleed air from the cooling system if your model requires it, then check for leaks and proper temperature operation.
- Dispose of used coolant responsibly at a recycling center or hazardous-waste facility.
Always follow the exact steps and safety guidelines in your owner's manual, and consult a qualified technician if you’re unsure about the process or the correct CES specification for your engine year.
Summary
The 6.7 Cummins calls for a long-life, ethylene glycol–based coolant that is phosphate- and silicate-free and specifically approved for Cummins engines or meeting Cummins CES standards. When in doubt, choose a Cummins-approved heavy-duty coolant, verify the exact CES specification for your model year, and follow the manual’s guidance on mixing and replacement intervals. Proper coolant selection protects the engine’s cooling system, maintains performance, and supports warranty compliance.
