The 6.7L Cummins runs an emissions system that puts real heat load on the cooling system, so coolant type and condition matter more than many owners expect. This guide covers the correct coolant, capacity and service approach. Refer to your owner's manual for the exact specification for your model year, since Ram revised recommendations across the 2007.5-present run.
What coolant the 6.7L Cummins uses
The 6.7L Cummins is factory filled with an organic-acid (OAT) coolant, commonly a fully formulated or extended-life diesel coolant.
- Type: an OAT diesel coolant meeting the Cummins/Ram specification, such as Fleetguard ES Compleat OAT or the Mopar equivalent; refer to your manual for the exact spec.
- Do not mix chemistries: mixing OAT with a conventional or hybrid coolant reduces protection and can cause deposits.
- Additive checks: with fully formulated coolant, verify additive levels on the recommended schedule.
System capacity
- Capacity: typically in the range of 5 to 6 gallons for the full system, varying by cab and configuration.
- Mix: a proper 50/50 concentrate-to-distilled-water ratio unless you buy premixed.
- Verify: always refer to your manual for the exact capacity and fill to the cold line.
The grid heater is not a glow plug
An important fitment note owners should know: the 6.7L Cummins uses a grid (intake air) heater, not glow plugs. The grid heater sits in the intake and warms incoming air for cold starts.
- No glow plugs: there are no glow plugs to buy or service on this engine.
- Cooling and the emissions system: the EGR system and regeneration cycles add heat, so a healthy cooling system supports the whole package.
Servicing the cooling system
- Interval: flush on the schedule in your manual; extended-life coolants run longer intervals but still need condition checks.
- Inspect: hoses, the pressure cap, the radiator and the water pump at service time.
- Watch for: overheating while towing, coolant loss with no visible leak, or a failing EGR cooler, which is a known concern on some 6.7L trucks.
Need a correct thermostat, water pump, EGR cooler, or coolant hose for your 6.7L Cummins? Email sales@coredieselparts.com with your VIN.
Frequently asked questions
What type of coolant does a 6.7L Cummins take?
An OAT (organic-acid) diesel coolant meeting the Cummins/Ram specification, such as a fully formulated extended-life product. Refer to your manual and keep the system on one chemistry.
How much coolant does a 6.7L Cummins hold?
Typically about 5 to 6 gallons for the full system, depending on configuration. Verify the exact figure in your manual and fill to the cold mark, then recheck after the engine cycles.
Does the 6.7L Cummins have glow plugs?
No. It uses a grid heater in the intake to warm the air for cold starts. If someone quotes glow plugs for a 6.7L Cummins, they have the wrong platform in mind.
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