The Cummins, Duramax and Power Stroke are the three diesel families found in American heavy-duty pickups. The Cummins is an inline-six used in Dodge and Ram trucks, the Duramax is a 6.6L V8 used in Chevrolet and GMC heavy-duty trucks, and the Power Stroke is a V8 used in Ford trucks across several generations and displacements. None of them is simply better than the others: each generation has its own strengths and its own commonly reported issues.
Cummins vs Duramax vs Powerstroke at a glance
| Engine family | Layout | Trucks | Displacements |
|---|---|---|---|
| Cummins | Inline-six | Dodge Ram and Ram 2500/3500 | 5.9L, then 6.7L |
| Duramax | V8 | Chevrolet Silverado HD and GMC Sierra HD | 6.6L across all heavy-duty generations |
| Power Stroke | V8 | Ford F-250/F-350 Super Duty and other Ford trucks and vans | 7.3L, 6.0L, 6.4L, 6.7L |
What is the difference between an inline-six and a V8 diesel?
An inline-six puts all six cylinders in one row with a single cylinder head. A V8 splits eight cylinders into two banks of four, each with its own head. The inline layout is longer and taller but has fewer heads, camshaft drive parts and gaskets to deal with. The V8 is shorter, which makes it easier to package in some engine bays, but it has two of many parts. Neither layout decides on its own how a particular engine will hold up; design details, model year and maintenance history matter more.
Cummins (Dodge and Ram)
Cummins is an independent engine maker, and its inline-six diesels have been offered in Dodge and later Ram heavy-duty pickups for decades. The 5.9L ran through mid-2007 in three broad versions: the mechanical 12-valve, the 24-valve, and the high-pressure common rail. The 6.7L replaced it for the 2007.5 model year and is also common rail. Our 12-valve vs 24-valve vs common rail guide explains how those versions differ, and 6.7 Cummins problems covers what owners of the newer engine commonly report.
Duramax (Chevrolet and GMC)
The 6.6L Duramax V8 arrived in GM heavy-duty pickups for the 2001 model year. It came out of a joint venture between General Motors and Isuzu. It has gone through several generations, usually referred to by their RPO codes (LB7, LLY, LBZ, LMM, LML and L5P), and parts are often specific to one code. GM also uses the Duramax name on a smaller 3.0L inline-six in light-duty trucks, which is a different engine from the 6.6L V8.
Power Stroke (Ford)
Power Stroke is the name Ford has used on several distinct diesel V8s rather than one engine that evolved. The 7.3L, 6.0L and 6.4L were supplied by Navistar (International), while the 6.7L that arrived for the 2011 model year was designed by Ford. Because these are separate designs, parts and repair knowledge from one Power Stroke generation usually do not carry over to another.
Do strengths and problems depend on the generation?
Yes. Owners of all three brands describe some generations as easy to live with and others as needing more attention, and the commonly reported issues on one generation can be absent on the next. Comparing “Cummins vs Duramax” or “Cummins vs Powerstroke” in general terms is less useful than comparing the specific engines in the specific model years you are considering, along with their service records.
Why must a replacement engine match the truck’s generation and emissions equipment?
Each generation uses its own mounts, wiring, sensors, fuel system and engine computer, so an engine from one generation rarely drops into a truck built for another. Emissions hardware changed as well: diesel particulate filters appeared across all three brands around the 2007.5 to 2008 model years, and selective catalytic reduction with diesel exhaust fluid followed in the early 2010s. A replacement should match the model year, the engine version and the emissions equipment the truck left the factory with.
- Confirm the engine by VIN and the engine data plate or tag, not by appearance.
- Decide whether you need a short block, long block or complete engine; each listing states which one it is.
- Check that the year range on the listing covers your truck.
We carry D&J short blocks, long blocks and complete engines for the Cummins only. Browse Cummins short blocks, long blocks and engines, or go straight to 5.9 Cummins engines or 6.7 Cummins engines and long blocks.
More guides: CP3 vs CP4 · how long diesel engines last · 6R140 problems · 5R110W problems · 6.4 Power Stroke problems · 5.9 vs 6.7 Cummins · how long a Cummins lasts · 68RFE vs Allison 1000.
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