This is the modern three-way that starts every diesel argument: Ford's 6.7 Power Stroke, Ram's 6.7 Cummins, and GM's L5P Duramax. All three are excellent, capable heavy-duty diesels, and none of them is a bad truck. The differences that matter to a buyer are in engine design, known weak points, and how each one fits the way you actually use a truck. Here's a straight, balanced comparison without brand cheerleading.
The three engines at a glance
- 6.7 Power Stroke "Scorpion" (2011 to present): Ford-designed 6.7L V8, notable for a reverse-flow head layout with the exhaust routed inward and the intake outward. It uses a high-pressure common-rail system, with the CP4.2 pump on 2011 and up. Ford has revised it across several generations, with output climbing significantly, especially the High-Output versions.
- 6.7 Cummins (2007.5 to present): the inline-six that Ram fans revere. A 6.7L I6 with a reputation for durability and simplicity relative to a V8. It used the Bosch CP3 pump through roughly 2018 and moved to the CP4 on 2019 and up.
- L5P Duramax (2017 to present): GM's 6.6L V8, a strong and refined engine. Notably, the L5P retained the more robust CP4-family setup in GM's own configuration and is known for a locked-down ECM that resists tuning.
All three make big power and torque and will tow anything a three-quarter or one-ton chassis is rated for. This isn't a capability contest; at stock, they're all more than enough.
Engine architecture: V8 vs inline-six
The Cummins is the odd one out, and for many buyers that's the appeal. An inline-six is inherently well-balanced, has fewer cylinders and injectors to service, and has a cult following built on the older 5.9's longevity. The tradeoff is packaging: the long six sits heavy over the front axle, which affects front-end feel and payload distribution compared to the V8s.
The Power Stroke and L5P are both V8s, more compact front-to-back and, many would argue, more refined in NVH and everyday drivability. The Power Stroke's reverse-flow head is a genuinely clever design that helps packaging and thermal behavior. The L5P is widely praised for smoothness and a strong stock tune.
There's no wrong answer here. It comes down to whether you value the inline-six's simplicity and reputation or the V8s' refinement and packaging.
Known weak points, honestly
Every one of these engines has something to watch:
- 6.7 Power Stroke: the CP4.2 injection pump is the headline concern. When a CP4 fails, it can send metal debris through the entire fuel system, an expensive event. It's not a frequent failure, but it's the one owners insure against. Watch EGT and exhaust sensors and keep the cooling system healthy.
- 6.7 Cummins: generally very durable, but the 2019-plus trucks introduced a grid-heater bolt that can loosen and drop into the engine, a known concern on that generation. Emissions hardware, EGR cooler, DPF, and SCR, needs maintenance like any modern diesel, and the CP4 on 2019-plus carries the same pump-failure consideration as the Ford.
- L5P Duramax: the most trouble-free of the three by reputation, but the locked ECM frustrates owners who want to tune, and CP4-related fuel-system caution applies here too. CCV service, fuel filtration, and coolant are the routine items.
The honest summary: all three are reliable when maintained, and all three share the modern common-rail reality that a fuel-system failure is the expensive worst case. Clean fuel and good filtration are cheap insurance on every one of them.
Which fits how you drive
- You want the inline-six mystique, simplicity, and a huge aftermarket: the 6.7 Cummins. Fewer injectors, a legendary reputation, and enormous parts support.
- You want strong integration, refinement, and a proven full-size heavy-duty package: the 6.7 Power Stroke, especially the later High-Output versions for max towing.
- You want the most trouble-free stock experience and don't care about tuning: the L5P Duramax, widely regarded as the most refined and reliable of the three out of the box.
Frankly, drivetrain aside, the truck around the engine, transmission, cab, ride, and how a given model year drives, often decides it as much as the engine. Test-drive all three at the trim and load you'll actually use.
The maintenance reality they share
Regardless of badge, these modern diesels reward the same discipline: fresh fuel filters at the correct interval, clean coolant, attention to the DEF and DPF systems, and not ignoring sensor codes. The fuel system is the expensive part on all three, so filtration and clean fuel are the single best habit you can build no matter which you buy. And none of these should be deleted or defeated, that's illegal on a road vehicle and tanks resale.
FAQ
Which is the most reliable, 6.7 Power Stroke, 6.7 Cummins, or L5P? The L5P has the strongest trouble-free reputation, and the Cummins is renowned for durability. The Power Stroke is a very strong engine with the CP4 as its main watch item. All three are reliable when maintained; there's no lemon in this group.
Is the Cummins better because it's an inline-six? It's different, not automatically better. The I6 offers simplicity, balance, and fewer injectors, but it's heavy over the front axle. The V8s are more compact and refined. Pick the tradeoff you prefer.
Do all three have the risky CP4 pump? The Power Stroke uses CP4.2 from 2011 up. The Cummins used CP3 through about 2018 and CP4 on 2019-plus. The L5P uses a CP4-family setup in GM's configuration. Clean fuel and good filtration reduce the risk on any of them.
Where we land
There's no loser here. Choose the Cummins for inline-six simplicity and aftermarket depth, the Power Stroke for refinement and top-end towing power, or the L5P for the most trouble-free stock experience. Then buy the truck on how it drives at your real load, and commit to fuel filtration and clean fluids, because that's what actually keeps any of these three alive.
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Related guides: - 5.9 vs 6.7 Cummins: Which Should You Buy? - Duramax Generations Compared: LB7 to L5P