If you ever want to start an argument between diesel enthusiasts, just bring up the subject of 6.7 Cummins and PowerStroke diesels and watch the sparks fly. It’s a rivalry as old as time itself. Both Cummins 6.7 liter turbo diesels and Ford Power Stroke engines are titans of the diesel world and are known for their prodigious torque, towing prowess and faithful fan following. One is an Indiana-born inline-six that’s a staple in Ram trucks, while the other is Ford’s beloved V8 seen in its Super Duty pickups. On paper, they have some similarities, but not much beyond their movements.
The Cummins 6.7-liter turbo diesel was introduced in 2007 as a replacement for the 5.9-liter turbo diesel that was a favorite among Ram pickups. You can even find it under the hood of the 2027 Ram Power Wagon, a diesel-powered off-roader. The 6.7 shared the robust cast-iron block of the 5.9, but featured performance advances and had longer service intervals. The engine received an update in 2013 that boosted torque while seeing a 10 percent improvement in fuel efficiency. For 2019, the fifth-generation Ram HD received a new engine block made from lighter compacted graphite iron and an updated fuel management system that pushed peak torque to over 1,000 pound-feet.
Meanwhile, the 6.7-liter Ford Power Stroke engine was introduced in 2011 as a replacement for the 6.4-liter Navistar engines. This was Ford’s automotive V8, code-named ‘Scorpion’, which had its own compacted graphite iron block alongside Bosch high-pressure fuel injection. Today, the engine pushes out nearly 1,200 pound-feet of torque.
Read more: There’s a good reason semi trucks don’t use V8s
Engine design
A Ram 3500 work truck outside at a dealership – Jetcityimage/Getty Images
The fundamental difference between Cummins Turbo Diesel and Ford Power Stroke comes from the number of cylinders and how they are arranged. The Cummins is an inline-six turbodiesel engine, meaning the six pistons sit in a straight line and atop a long crankshaft. Inline six engines are some of the best balanced, given that their piston placement inherently cancels out both primary and secondary vibrations. Because it uses fewer pistons than the Ford V8 6.7, it has massive pistons and a comparatively larger bore and stroke. It also offers lower grunt, making it ideal for towing applications. The engine layout also gives it an understressed nature, meaning that with proper maintenance, Cummins power plants can easily go a million miles.
The Ford PowerStroke is a V8 turbo diesel with four cylinders per bank and a shorter crankshaft. It is also somewhat more complex than the Cummins. The engine has a reverse flow manifold design, which is different from a traditional V8. The latter has the exhaust manifold on the outside of the engine banks, while the Ford has an exhaust outlet from the engine valley, directly into the turbocharger. This reduces turbo lag and makes the engine quite responsive. While both engines run compact graphite cast iron cylinder blocks, the Cummins uses a traditional cast iron cylinder head, while the Power Stroke uses lighter aluminum cylinder heads.
Performance stakes
A Cummins turbo diesel logo on a vehicle – Around the World Photos/Shutterstock
In diesel vehicles, the most important statistic is torque. Both 6.7 engines offer prodigious amounts of torque here, but they differ in how they deliver it, with the Ford 6.7 Power Stroke topping the performance charts. In High Output trim found on top Ford Super Duty trucks, the V8 turbo diesel engine pushes out 500 horsepower and 1,200 pound-feet of torque. However, the 6.7 Cummins turbo diesel isn’t far behind in the performance stakes, offering nearly 430 horsepower and 1,075 pound-feet of torque. It should be noted that despite its simplistic construction, even its early iterations produced a formidable 370 horsepower and 850 pound-feet of torque.
Peak horsepower and torque numbers tell only part of the story. The Cummins engine delivers its torque across a wider rpm range thanks to its inline six and turbo configuration. This allows it to effortlessly pull heavy loads even on steeper slopes, while the Power Stroke does it with brute force. Its peak power is delivered at a slightly higher rev with more aggressive power delivery, especially in the High Output engine configuration. When it comes to the real world, however, both engines deliver. With its extra torque, the Power Stroke has a slight edge when it comes to peak ratings, but that hasn’t stopped people from loving the Cummins alternative.
The deep end
A Ford Power Stroke V8 diesel engine under the hood of a vehicle – Hrach Hovhannisyan/Shutterstock
Reliability, longevity and durability form the baseline for these types of engines. 6.7 Cummins has a long-standing reputation for bulletproof longevity. Much of this reputation is due to its simple yet robust architecture, but other considerations make it a favorite among long-haul fleets and heavy commercial users. Six-in-line configurations leave plenty of room, making repairs and diagnostics easier. These engines also use the Bosch CP3 high-pressure fuel pump for the 6.7, apart from a brief period (2019-2020) when they switched to – and reverted from – the not-so-reliable Bosch CP4.2.
The early 6.7 Power Stroke engines had some starting problems with their high pressure fuel pumps and turbochargers. (According to the owners, these are the worst years for the Ford 6.7 Power Stroke.) These engines have always used Bosch CP4.2 pumps which were known for their aversion to poor quality fuel. Newer generation Power Stroke engines (2015 onwards) addressed most of these concerns and featured improved durability and reliability. In terms of functionality, however, the layout of the Ford V8 engine limits easy access to certain areas. However, compared to Cummins, Ford’s massive dealer network means you’ll find help even in the most remote regions.
While real-world feedback pushes Cummins ahead in the durability stakes, modern Power Strokes are also pretty reliable. Diesel forums indicate that both engines will exceed the 300,000 mile mark – provided they are properly maintained. Under normal usage, most users won’t even go so far as to stress these motors anyway. All they need is emissions related maintenance such as periodic DPF regeneration and EGR cooler cleaning.
Driving experience
A Ford F-550 Power Stroke engine under the hood – JoshBryan/Shutterstock
Cummins users are generally impressed that ample torque is quite accessible even at low revs, giving it the ability to pull heavy loads with minimal fuss. However, its towing speeds are somewhat limited by the lack of gears in the six-speed transmission. The Power Stroke engines feel more eager off the line because of their big power and how they’re paired with the 10-speed automatic transmission, which also adds massively to their towing capabilities.
In terms of fuel economy, the Cummins engine offers comparatively lower mpg while pulling heavy loads. This is not as bad as it sounds, as some Cummins engines can even run on biodiesel. But the 6.7 Power Stroke offers better fuel economy when driving under load and on the highway.
As for the driving experience, the Cummins engine setup gives it an old-school diesel rumble, while the Ford’s V8 setup emits a roaring growl. With their emissions control systems wiped, you’d notice that the Cummins sounds like an old tractor, while the Power Stroke sounds like a jet engine. Overall, both engines are towing champions, but the Cummins rigs feel like proper work trucks, while the Power Stroke trucks feel like performance vehicles.
The better choice
A Dodge 3500 with an exposed Cummins engine – Hrach Hovhannisyan/Shutterstock
There is no absolute champion here. The 6.7-litre Cummins Turbo Diesel engine has built a reputation for long-haul durability and effortless, linear torque delivery under heavy load. It has a simpler engine architecture with solid internals that boasts a proven track record for reliability and functionality. Cummins is the purist’s choice when it comes to powertrain – a commercial engine that has found its way into a truck. It revs slow, noisy, heavy, and might even resist you.
In comparison, the Ford Power Stroke 6.7 feels like an extra-capable beast when you factor in speed, refinement and built-in technology. Compared to the raw and rugged nature of the Cummins engine, the Ford V8 is quieter and more sophisticated. The V8 diesel engine paired with the 10-speed transmission makes for a ridiculously quick ride, and when it comes to towing, it’s an effortless experience too.
While the Cummins feels like the Old Testament of diesel engines, the Ford Power Stroke feels like the future. If you’re looking for a proven workhorse, the Ramul with a Cummins engine is your best bet. If you want a fast pickup truck that can also tow houses if need be, the Ford Super Duty should be right up your alley—even with the other compelling engine option, the 7.3-liter gasoline-powered Godzilla V8.
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