Duramax vs. Cummins: Everything You Need to Know

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Duramax and Cummins are two of the leading manufacturers of diesel engines, catering to a wide range of makes and models. However, they feature key differences in performance and reliability that can affect your decision when choosing between Duramax and Cummins. Learn how these brands compare in towing, efficiency and reliability.

Duramax vs. Cummins: An Overview

Produced by General Motors, Duramax engines first hit the market in 2001. They power GMC and Chevy trucks, including the Chevy Silverado and GMC Sierra, and work with automatic transmissions. The latest iteration, the L5P, has been around since 2016 and gets up to 470 horsepower at 2,800 RPM and 975 lb.-ft. of torque at 1,600 RPM. Duramax uses common rail injection to improve injection pressure and timing. Instead of relying on mechanical inputs, the injection system uses electronic sensors to send pressurized fuel to the injectors. 

Stellantis-made Cummins engines are used in RAM diesel trucks. The brand is over a hundred years old and has been perfecting the injection process ever since. The latest High-Output 6.7-liter engine gets up to 420 horsepower and 1,075 lb.-ft. of torque. It uses a variable-geometry turbocharger that adjusts the amount of compressed air entering the combustion chamber based on the required power output. VGT turbos result in better fuel efficiency than fixed-geometry turbos.

Duramax vs. Cummins: Maintenance

Duramax and Cummins engines are revered for their durability, lasting up to a million miles with proper maintenance. However, Cummins engines get higher marks for their simplicity and ease of use. They contain fewer parts than Duramax engines, leading to fewer complications. Duramax features cast aluminum cylinder heads, while Cummins uses cast iron, which is more durable when faced with extreme temperatures. 

All diesel engines require regular oil changes, filter replacements and pressure monitoring to detect and prevent blockages that reduce efficiency. The injection system pressurizes the fuel using oil before sending it to the injectors. Carbon buildup, sensor errors and oxidation reduce fuel pressure, reducing power and your MPG rating. Shop for replacement diesel parts by engine model to maintain your specs.

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Duramax and Cummins engines use exhaust gas recirculation (EGR) to reduce harmful emissions. They recycle part of the exhaust gas by sending it through a cooler before returning it to the combustion chamber instead of releasing it out the tailpipe. Excess towing and high temperatures can cause the EGR to leak coolant into the crankcase. Replace the EGR cooler if the engine overheats, the vehicle loses efficiency or blue smoke emits from the exhaust. 

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Duramax vs. Cummins: Towing, Power and Efficiency

Looking at the numbers, Cummins leads Duramax in terms of torque, but the difference is negligible across most models. You’ll also need to max out your towing package and choose the High Output Cummins 6.7-liter option to get four-digit torque.

Duramax bests Cummins in horsepower, reaching 470 HP over 420. However, Cummins engines are known for better low-end torque, which is crucial for safely towing heavy loads from rest and loading/unloading at specific locations. 

The Duramax also leads Cummins in MPG ratings, but efficiency ratings vary widely from model to model. The Chevy Silverado 1500 gets up to 23 MPG in the city and 29 MPG on the highway, while the RAM 2500 gets 14 MPG in the city and 17 MPG on the highway.

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Choosing Between Duramax and Cummins

Both options provide some of the best torque and horsepower on the market, but choosing between the Duramax and Cummins depends on model specifications and your priorities as a driver. Cummins is better for towing heavy loads from rest, but Duramax engines produce more power per gallon of fuel. Remember these differences to find the best pick-up truck for your next job.

Considering a Ford Powerstroke engine instead? Use this Duramax vs. Powerstroke guide to see how the latest RAMs compare to Ford pick-up trucks.