Is the Cummins 6.7 a good engine?
Yes. The Cummins 6.7L inline-six is widely regarded as one of the most durable and capable diesel engines in heavy-duty pickups, delivering strong torque and long service life when properly maintained.
In this report, we explore what the engine is, how it has evolved across generations, what owners can expect in terms of performance, reliability, and maintenance costs, and how it stacks up for diverse use cases—from daily driving to serious towing.
Overview: what the Cummins 6.7 is and where it powers Ram trucks
The Cummins 6.7L inline-six, commonly referred to as the ISB6.7, has been a cornerstone powerplant for Ram’s heavy‑duty pickups, including the 2500 and 3500 lines. It is a turbocharged diesel designed to deliver high torque at low RPM, which makes it well-suited to towing and heavy payload work. Over the years, Ram offered standard and high‑output calibrations to suit different tasks—from everyday driving to maximum towing capability—with the high‑output variant providing more horsepower and torque for demanding applications.
Performance and capability
Power, torque and drivability across generations
There are notable variations by year and configuration:
- Early ISB6.7 models (approx. 2007–2012) typically offered around 350–370 horsepower and 650–800+ lb-ft of torque, prioritizing reliability and durable towing.
- Mid‑generation updates (approx. 2013–2018) increased torque further, with horsepower commonly in the 370–385 hp range and torque extending into the 800–900+ lb-ft range depending on emissions tuning.
- High‑output versions (around 2019 onward) tune for heavier use, with about 420 horsepower and up to about 1,000 lb-ft of torque, enabling significantly higher tow ratings on 3500 models.
In daily operation, the engine delivers strong low‑end torque and a broad, usable torque curve, which helps with acceleration and hill climbing when towing. The turbocharged setup and Cummins reliability combine to provide confident, predictable performance across a wide range of loads.
Fuel economy and operating costs
Diesel powertrains generally offer better highway efficiency than gas engines for similar weight classes, but the 6.7L remains a heavy‑duty diesel, so fuel economy is modest compared with lighter vehicles. Real‑world figures vary with payload, towing, terrain, and driving style, but owners typically see mid‑teens to the low‑20s mpg on highway trips when not towing, with lower figures when pulling heavy trailers. Maintenance and operating costs include diesel fuel, DEF, regenerative exhaust systems, and periodic service of high‑pressure fuel components and the turbocharger.
Reliability and maintenance considerations
The 6.7L Cummins has a strong durability record, especially when owners adhere to manufacturer‑recommended maintenance and use quality parts. Long‑term reliability is aided by a robust engine design, good aftermarket support, and a track record of heavy‑duty service. Regular maintenance—oil and filter changes with appropriate diesel oil, fuel filter service, coolant checks, and attention to the emissions system—is essential to maximize lifespan.
What to watch for over the life of the engine
As with any modern diesel, several item groups deserve attention as mileage climbs:
- Emissions system components (DPF, DEF system, EGR) and associated sensors; failures can trigger limp modes or reduced performance if not addressed.
- High‑pressure fuel system components and injectors, which can wear with high mileage or low‑quality fuel and may require service or replacement.
- Turbocharger wear or boost control issues, particularly in high‑mileage trucks or those operated at high loads for extended periods.
- Cooling system integrity and potential leaks, as engine and turbo temperatures rise under heavy towing.
Proactive maintenance, using proper fluids and Patrick‑level service from qualified technicians, helps minimize these risks and keeps the engine performing at a high level for years.
Pros and cons
Before weighing ownership, here are the engine’s core advantages and potential drawbacks:
- Pro: Exceptional low‑end torque makes it outstanding for towing heavy trailers and hauling loads.
- Pro: Strong durability and a large, active parts and service ecosystem support long‑term ownership.
- Pro: The high‑output variant provides maximum torque and horsepower for the most demanding tasks.
- Con: Higher maintenance and operating costs than typical gasoline engines, including diesel fuel and DEF/SCR system upkeep.
- Con: Emissions‑control components add complexity and potential failure points that require ongoing attention.
- Con: Repairs to high‑pressure fuel system components can be expensive, particularly out of warranty.
With disciplined maintenance, the 6.7L Cummins remains a dependable workhorse in the heavy‑duty segment.
Is it a good engine for you?
If you need serious towing capability, heavy payload capacity, and a durable long‑haul powertrain, the 6.7L Cummins is a strong choice within Ram’s heavy‑duty lineup. It excels in workhorse roles and long‑term ownership, backed by a robust parts network and proven performance. If you don’t tow frequently or prioritize ultra‑low operating costs or simplicity, you might evaluate less complex or lighter‑duty options, but for demanding applications the 6.7 is widely regarded as one of the best in its class.
Summary
The Cummins 6.7 is revered for its torque, durability, and proven track record in Ram heavy‑duty pickups. With proper maintenance, it delivers reliable performance for towing and demanding work, supported by a broad ecosystem of parts and technicians. While ownership carries higher diesel costs and emissions‑system maintenance, the engine’s longevity and capability make it a strong, industry‑standard choice for buyers seeking a true workhorse powerplant.
Bottom line: it remains a good engine for those who need heavy‑duty capability and long‑term reliability, provided maintenance is kept up and the truck is used within its intended duty cycle.
