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When it comes to diesel truck engines, there are two names that lead the pack: Duramax and Cummins. Duramax diesel engines are usually found in General Motors and Chevy trucks, while Cummins typically supports Fiat Chrysler’s Ram truck line and the Nissan Titan.
It can be a struggle to decide which engine to choose. Fortunately, there is no wrong answer. Neither engine is better than the other, but they do have distinct similarities and differences.
We’ll compare both diesel engines and help you make a decision.
2007 GMC Sierra 2500HD SLE Crew Cab 6.6L LBZ Duramax – Image courtesy of and copyright of Bring a Trailer
Duramax began with a partnership between companies General Motors and Isuzu. The first generation of Duramax engines launched in 2001. At the time, Duramax engines offered 520 pounds-feet of torque. New LB7 Duramax parts included parts that Cummins didn’t start using until 2003, including the high-pressure, common-rail Bosch CP3 injection pump.
Since its initial release, there have been many different updated models for the Duramax engine. In 2004 came the Duramax LLY, then the LBZ engine in 2006. Duramax quickly got another update when the Duramax LMM came out in the middle of 2007. After that, the LML arrived in 2011. Duramax didn’t see another revision until 2016 when the more powerful Duramax L5P was launched.
2011 Ram 3500 ST Crew Cab Cummins 6.7L 4×4 6-Speed – Image courtesy of and copyright of Bring a Trailer
The Cummins brand is much older than Duramax. The engine’s inception began in 1919 –more than 100 years ago. The Chrysler Corporation has been using Cummins engines in their Rams since 1989. Meanwhile, GM has only been using the Duramax engine since 2001, a little more than 20 years ago. If you think a long-established brand is important, then the history behind Cummins will appeal to you.
The first Cummins diesel engine used in a Ram truck was the 5.9 six-cylinder turbodiesel, which was capable of 400 pound-feet of torque. Ford and Chevy were also using diesel engines during the Cummins’ launch, but the Cummins engine changed the market by including a turbocharger, direct injection, and 400 lb-ft torque, something no other engine offered at the time.
In 2007, the 5.9-liter Cummins engine was replaced with the 6.7-liter engine.
The 6.7 engine parts were similar to the 5.9 Cummins parts, but the engine had been redesigned to meet new emissions standards. This new engine offered more torque –650 pound-feet of it– while running half as loud.
Diesel trucks are renowned for their towing abilities. Many people buy diesel trucks to help them carry heavy equipment, such as trailers, campers, and boats. A diesel engine’s power comes from its torque: you need lots of torque to handle heavy equipment, and a diesel engine produces much higher torque than a gas engine.
How much torque a Duramax engine or a Cummins engine provides varies from truck to truck. For example, a GMC Sierra HD with a Duramax 6.6-liter diesel engine will produce 910 pound-feet of torque. Compare that to a Nissan Titan XD with a Cummins 5.0-liter diesel engine, which makes 555 pound-feet of torque. However, the 6.7-liter Cummins engine in a 2018 Ram Heavy Duty truck will generate 930 pound-feet of torque.
From 2001 to 2004, the Duramax 6.6L LB7 was capable of 520 pound-feet of torque. By mid-2007, the Cummins 5.9-liter engine was capable of producing 610 pound-feet of torque, while the Duramax 6.6L LMM was putting out 650 pound-feet of torque. In recent years the engines now maintain similar specifications.
Torque is the most important factor in determining towing capacity, but horsepower is also up there. The more horsepower an engine has, the faster it can accelerate. Which engine has the highest horsepower? The current Duramax engine, the Duramax 6.6L L5P, produced the most at 445 horsepower. In comparison, the most recent Cummins engine, 6.7L 24V Ram Cummins, produces 400 horsepower. Duramax diesel engines have a reputation for offering slightly more horsepower than Cummins engines.
How do the engines compare in specs? The current Cummins engine is a 6.7-liter inline-six, while the Duramax is a 6.6-liter V8. Duramax offers more horsepower, but Cummins provides the most torque. Depending on the truck, a Cummins engine can provide up to 1,000 feet-pounds of torque.
Here are other specs to consider when choosing an engine:
When it comes to towing, Cummins engines are king. However, most passenger and light work trucks don’t need to tow as much weight as a Cummins engine can. To meet your average, everyday needs, both Cummins and Duramax engines are capable of giving you enough towing power. Choosing an engine largely depends on which truck you want.
Whatever engine you choose, remember to use ProSource for all your diesel truck parts needs, including Dodge diesel parts and GM Duramax parts.
