Diesel engines are as popular in name as the vehicle manufacturers who produce them. General Motors’ (GM) Duramax, Ford’s Power Stroke, and Stellantis’ (Ram) Cummins are the three dominant names in the American diesel truck market. Each diesel engine offers particular advantages over the other, but overall, diesel motors are sought after for their low-end torque figures, trailer towing pulling power, and longevity over traditional motors.
Power and longevity are not the only two factors at play, though. Since each engine comes from a different manufacturer, there are inevitable design differences. Additionally, there are staunchly loyal fans of each of the three engines and manufacturers.
The best diesel engine option for consumers is ultimately the one that best fits their daily needs. Generally speaking, all three engines will provide most customers with the capability they need to perform their everyday tasks. When it comes to pushing the limits, though, all three have their own sets of pros and cons.
The largest difference between the three diesel engines is each one’s torque figure. Ford’s Power Stroke Diesel leads the way with 1,050 lb-ft of torque. A high-output version of the same engine produces an even higher torque figure: 1,200 lb-ft. Chevy’s 6.6-liter Duramax Diesel produces 975 lb-ft of torque and the high-output 6.7-liter Cummins diesel, used in RAM trucks, produces up to 1,075 lb-ft of torque.
The second largest difference between the three diesel engines singles out the Cummins from the other two competitors. It is the only inline-six of the group. Both the Power Stroke and Duramax feature V8 layouts. Even though it is a notable difference, it should also be noted that most commercial trucks today are equipped with inline-six diesel engines rather than V8s, making the Power Stroke and Duramax options rather anomalous when it comes to trucking.
Horsepower ratings are the third difference between the three rivals. Ford’s Power Stroke again leads the pack with up to 500 horsepower in its high-output form. The 6.6-liter Chevy Duramax produces 470 horsepower, and the high-output Cummins produces 420 horsepower. As such, Ford Super Duty trucks lead the way when it comes to towing, with a claimed maximum towing capacity of up to 40,000 pounds with a gooseneck trailer with its high-output diesel engine.
Lastly, each engine is marked by its history. Cummins wins here with a history dating back to the late 1910s. Although their current B Series family of engines has only been around since 1984, Clessie Cummins started his company alongside William Glanton in 1919. The Power Stroke name has been around since 1994, and Duramax, the newest kid on the block, started production of its engine alongside Isuzu in 2000.
The latest 6.6-liter V8 Chevy Duramax Diesel engine, used in Chevrolet Silverado HD and GMC Sierra HD pickup trucks, produces 470 horsepower and 975 lb-ft of torque.
This engine should not be confused with the smaller 3.0-liter inline-six Duramax Turbodiesel available in the Chevy Silverado 1500, GMC Sierra 1500, Chevy Tahoe, Cadillac Escalade, and Chevy Suburban.
General Motors’ heavy-duty trucks, including the 2024 Chevrolet Silverado 2500HD, 2024 Chevrolet Silverado 3500HD, 2024 GMC Sierra 2500HD, and 2024 GMC Sierra 3500HD, all feature the latest version of the 6.6-liter Duramax Diesel as an option across all trim levels. The engine is paired with a 10-speed Allison transmission, and the two lowest trim levels on each model even come with an optional integrated PTO.
Known as the L5P Duramax, the 2024 version has been improved over the 2023 version. It is more powerful than before, it benefits from an updated variable geometry turbocharger, it features an updated piston design, it receives higher-flow fuel injectors, and it gets upgraded valve springs, all helping increase the engine’s capability, efficiency, and fuel economy.
The L5P features a cast iron engine block, a cast aluminum cylinder head, a high-pressure, common rail fuel system capable of 32,000 psi, an exhaust brake, and cold-start technology to assist the engine starting in cold temperatures.
Maximum towing capacity comes in at 36,000 pounds on a properly equipped Chevy Silverado 3500HD. Silverado 2500HD models have a lower towing capacity, capped out at 22,500 pounds.
The Duramax 6.6-liter’s largest advantage over RAM’s Cummins and Ford’s Powerstroke is that it slots right in between its competitors in terms of power and towing. That gives it the advantage of treading a good middle ground for buyers who want both a healthy horsepower number and the ability to tow.
Even though the EPA does not require fuel economy testing for these trucks, the Duramax is known to be quite fuel efficient compared to the Cummins and Power Stroke. Additionally, having been thoroughly updated for the 2024 model year with several upgrades, it is the freshest of the three diesel engines.
If size truly does matter, the Duramax cannot deliver. It has the smallest displacement of all the heavy-duty turbo diesel engines on our list, albeit only by a small margin. There is also no high-output version like the Cummins and Power Stroke have. When comparing both high-output engines to the only Duramax option, it falls to both in terms of torque.
Unfortunately, it is also a bit pricey to get into a base Silverado 2500HD or 3500 HD compared to the Ford and RAM. A base Silverado 2500HD model starts at around $57,000. A base Silverado 3500HD starts at around $58,700. A comparable base F-250 with the standard 6.7-liter Power Stroke starts closer to $55,000 while a RAM 2500 also starts around $55,000. Jump up to the F-350, and you can expect to start at around $56,000.
Additionally, if history is important to you, the Duramax may not meet your expectations. They have made good diesel engines in the past, but they have only been doing it since the beginning of the 2000s, less time than both competitors.
Two versions of the 6.7-liter Cummins Turbo Diesel are available in current RAM heavy-duty pickup trucks. Unlike the Power Stroke and Duramax Diesels on this list, it is built as an inline-six rather than a V8 and produces two sets of power figures depending on its accompanying transmission.
The less powerful version produces 370 horsepower and 850 lb-ft of torque. The more powerful, high-output version produces 420 horsepower and 1,075 lb-ft of torque.
Cummins diesel engines have a long history with RAM pickup trucks, being utilized by them when they were still affiliated with Dodge. The 5.9-liter B-Series Cummins engine, used in the Dodge RAM pickup truck starting in 1989, is perhaps the most well-known diesel to ever be used in a pickup truck. To this day it is known as one of the most reliable diesel engines ever used in a pickup truck application, often outlasting the rest of the truck in which it came.
Today, the 370-horsepower 6.7-liter Cummins diesel can be found in all RAM 2500 models with the exception of the Power Wagon. It comes paired with a six-speed automatic transmission rather than the standard eight-speed found in the RAM’s non-diesel engines.
The more powerful 420-horsepower high-output 6.7-liter Cummins diesel can be found in RAM 3500 models. It comes with an upgraded heavy-duty Aisin transmission, still with six speeds.
Both engines feature a Bosch high-pressure common rail fuel system, a Holset variable geometry turbocharger, a compacted graphite iron engine block, cast iron cylinder heads, an exhaust brake, and heavy-duty engine cooling. Properly equipped RAM3500 models can tow just over 37,000 pounds while properly equipped RAM 2500 models max out at just under 20,000 pounds.
Many of Cummins’ strengths can be attributed to its inline-six layout. Even though its displacement is right in line with the others, it does not have any banking, ultimately making it less compact, at least from a width perspective. Both V8s on this list are much wider because of their “V” configuration.
Inline-six engines also tend to be smoother than V8s because of their inherent balance. V8s can be smooth, but they must utilize balance shafts to do so. An inline-six, therefore, will typically experience less wear and tear over time as a result.
Thirdly, inline-six engines tend to make low-end torque easily, even compared to the other V8s on our list. This is evidenced by the high-output Cummins engine that produces 1,075 lb-ft of torque, even though its power figure is lower than its competitors. This is due to its longer stroke within the engine block.
Lastly, Cummins has a long history of making engines. If heritage is important to you, Cummins will fit the bill with its more than 100 years of experience as a company.
The Cummins has two major drawbacks. First, it is the weakest in terms of horsepower when comparing both regular and high-output engines, and it features the lowest torque figure when considering the non-high-output engines. Being the weakest of the three may not usually matter since 370 horsepower and 850 lb-ft of torque is plenty for most people, but if maximum towing is your ultimate need, both rivals can provide more.
Secondly, because of its length and lack of natural lateral rigidity, the torsional forces exerted by the engine’s components over time may lead to extra wear and tear. Even though the inline-six is smooth, it is not as inherently rigid.
Ford’s most current 6.7-liter Power Stroke Turbo Diesel engine comes in two forms, similar to the Cummins. The less powerful version of the engine makes 475 horsepower and 1.050 lb-ft of torque. It comes optional on all Ford F-250 and F-350 models except for the top-of-the-line Limited trim level. It also comes standard on each Ford F-450 trim level except the Limited.
Ford F-250, F-350, and F-450 Limited models come standard with the high-output Power Stroke engine, producing 500 horsepower and 1,200 lb-ft of torque. Each 6.7-liter Power Stroke is mated to Ford’s TorqueShift ten-speed automatic transmission.
The Power Stroke Turbo Diesel features a Garrett variable geometry turbocharger, a Bosch-sourced high-pressure common rail fuel system, forged steel pistons, a compacted iron graphite engine block, aluminum cylinder heads, and an instant glow plug system. The high-output version of the Powerstroke differs only slightly from the standard engine, featuring larger exhaust manifolds and a PCM tune to increase its power output.
When properly equipped, a 2023 Ford F-450 equipped with the high-output Power Stroke can tow 40,000 pounds with a gooseneck trailer.
The Power Stroke’s most obvious advantage is its ceiling of power. With the few updates made to the engine in the past year, both power and torque are class-leading, particularly with the high-output engine. If towing capability is what you need, the 6.7-liter Power Stroke can get you there.
Additionally, you will tend to pay a little less to get one than you will the other two. A base model Ford F-250 or F-350 with the base Power Stroke costs about the same or less than both of its competitors. That may change as you add options and walk through the trim levels since each truck has its own set of trims and feature options.
Like the Duramax engine, the Power Stroke engine has been around the block, but not nearly as long as the Cummins has. It again does not have the long history of engine making that could be important to certain buyers.
Secondly, because of its position as the most powerful engine on our list from the factory, it also stands to reason that its engine components could also experience the most wear and tear from the power that it makes. Diesel engines are known for their longevity because of their “laziness” as compared to gasoline engines. The high-output Power Stroke, though, is making more horsepower and torque with the same displacement as its rival engines.
That may not ultimately contribute to reliability issues down the road, but it does mean that there is at least some level of added pressure within the engine and to its components, regardless of how strong they are.
Which of the three diesel engines is right for you? Ultimately it comes down to your own wants and needs. Even though the high-output Power Stroke is the most powerful, the non-high output Power Stroke, the non-high output Cummins, and the Duramax are all fairly close in terms of power production.
It is just as likely that someone could buy a RAM truck over the Ford or Chevy because they are partial to Cummins Diesel engines. A Ford or Chevy loyalist is most likely going to choose the Silverado 2500HD or F-250 over a RAM 2500 simply because they prefer Ford or Chevy over RAM, regardless of each truck’s power figures.
Still, each engine does bring its own unique set of pros and cons to the table, and if you fall under the undecided umbrella, you can now decide which diesel engine is right for you based on what each of them offers.