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The Cummins diesel engines boast a worldwide reputation for bulletproof durability. In fact, some 30-year-old Cummins-powered high-mileage Ram trucks command new truck prices. So, what is considered high mileage for a Cummins engine?

How long does a Dodge Cummins last?

A properly maintained Cummins engine can last 300,000-350,000 miles. But a poorly treated truck can wear out much sooner. Therefore, a diesel truck with proper service records or even one that received precise “fleet” maintenance commands a premium.

Detail shot of a Cummins Turbo Diesel badge on the Fender of a Ram 3500 truck.
2022 Ram Cummins Turbo Diesel badge | Stellantis

The Cummins 6BT is an inline six-cylinder turbocharged diesel engine. And it was never intended for use in a pickup truck.

By the mid-1980s, the General Motors and Ford diesels boasted the power and fuel efficiency to make them best sellers. But Dodge did not yet have a diesel option in its pickups, so Dodge approached Cummins about its recently-engineered 6BT.

The 5.9-liter diesel engine had been engineered for use in construction and agricultural equipment. With harsh use in mind, Cummins had overbuilt every aspect of the powerplant.

Dodge was able to redesign its Ram 250 and 350 trucks for the heavy-duty powerplant. The resulting truck was an instant sales success and is still sought-after today.

What is high mileage for a 5.9 Cummins?

From 1989 through 2006, Cummins offered a 5.9-liter I6 diesel for Ram truck buyers. The pre-1998.5 (often referred to as 12-valve or 12v) engines are especially prized for their reliability. But most well-maintained 5.9-liter engines don’t need a major overhaul for 300,000 miles. Some last much longer.

Render of a transparent Ram 3500 pickup truck, its Cummins diesel drivetrain visible.
2022 Ram 3500 Cummins powertrain | Stellantis

Some mechanics prefer the simplicity of the pre-1998.5 12-valve Cummins engines. But some drivers prefer the power and fuel efficiency of the later 24-valve 5.9-liters (halfway through 1998-2006).

Well-maintained 5.9-liter engines offered good enough durability to build Cummins an incredible reputation. The Cummins company has even created a high mileage club for owners whose trucks have exceeded 100,000 miles. It has more than 20,000 members.

What is high mileage for a Cummins 6.7 diesel?

For 2007, Cummins increased its 6BT’s displacement to 6.7 liters to produce the same amount of power while meeting emissions standards. The 6.7 Cummins’ electronic control system enables the engine to make more power at lower RPMs while burning less fuel. Maintenance may be more expensive than for the 5.9, but the well-cared-for 6.7 can still last 300,000 miles without a major rebuild.

Promo shot of a 6.7-liter Cummins turbo diesel engine.
6.7-liter Cummins turbo diesel | Stellantis

For the 2022 model year, Cummins offers two tunes of its 6.7-liter turbo diesel. The regular “standard output” engine makes 370 horsepower and 850 lb-ft of torque. The “high-output” version of the Cummins is available in the Ram 3500. It can make 420 horsepower and an incredible 1,075 lb-ft of torque.

Ram Trucks is so confident in the durability of its latest generation Cummins engines that it doesn’t recommend you change the oil more than every 15,000 miles. That’s the longest intervale in the heavy-duty class.

Next, find out whether Cummins 1,000-horsepower military-spec I4 would fit in your truck or, see the difference between a high and low-mile truck in the video below: