Diesel Truck Engines Compared: Cummins, Duramax, Power Stroke

12 heavy-duty diesel generations in the Ram 2500/3500, Ford Super Duty and Silverado / Sierra HD, matched to 24,426 owner complaints by VIN. The 6.0 Power Stroke draws the biggest share of engine complaints (34%), the 5.9 Cummins the smallest (4%).

Every generation, side by side

Engine	Years	Complaints	Name the engine	Name the fuel system	Stalled or lost power	Recalls naming it
6.0 Power Stroke	2003–07	1,708	34%	16%	31%	2
6.4 Power Stroke	2008–10	572	28%	7%	11%	2
Duramax L5P	2017–26	1,229	16%	10%	14%	2
7.3 Power Stroke	1999–03	2,049	15%	5%	12%	1
Duramax LML	2011–16	779	13%	20%	17%	0
6.7 Cummins	2007–26	7,667	11%	8%	6.4%	9
6.7 Power Stroke	2011–26	5,640	10%	11%	7.8%	6
Duramax LBZ	2006–07	186	8%	5%	7.0%	0
Duramax LMM	2007–10	385	8%	6%	5.2%	0
Duramax LB7	2001–04	592	7%	17%	5.4%	1
Duramax LLY	2004–06	374	7%	11%	7.8%	0
5.9 Cummins	1999–07	3,245	4%	7%	5.0%	0

Each column is a share of that engine's own complaints (VIN-matched), so popular engines don't win just by selling more. None of these is a failure rate: no one reports HD sales by engine.

Engines to check hardest

Known problems that stand out in owner complaints (at least 1.5× the median of the other generations, 10+ complaints):

7.3 Power Stroke: stalling (often the cam sensor), 242 of 2,049 complaints (12%) against a 7.8% median.
6.0 Power Stroke: head gaskets, 52 of 1,708 complaints (3.0%) against a under 0.1% median.
6.0 Power Stroke: the EGR cooler / valve, 150 of 1,708 complaints (8.8%) against a 0.3% median.
6.0 Power Stroke: the oil cooler, 47 of 1,708 complaints (2.8%) against a under 0.1% median.
6.0 Power Stroke: injectors, 157 of 1,708 complaints (9.2%) against a 1.2% median.
6.4 Power Stroke: radiator and coolant leaks, 16 of 572 complaints (2.8%) against a 0.8% median.
6.4 Power Stroke: the DPF / regen system, 13 of 572 complaints (2.3%) against a 0.1% median.
6.7 Power Stroke: the CP4.2 high-pressure fuel pump, 172 of 5,640 complaints (3.0%) against a 0.3% median.
6.7 Power Stroke: the DPF / DEF / NOx sensors, 147 of 5,640 complaints (2.6%) against a 0.1% median.
5.9 Cummins: injectors, 81 of 3,245 complaints (2.5%) against a 1.2% median.
6.7 Cummins: the DPF / EGR / DEF system, 164 of 7,667 complaints (2.1%) against a 0.1% median.
6.7 Cummins: the turbo, 129 of 7,667 complaints (1.7%) against a 1.0% median.
Duramax LB7: injectors, 72 of 592 complaints (12%) against a 1.2% median.
Duramax LLY: overheating when towing, 16 of 374 complaints (4.3%) against a 0.8% median.
Duramax LLY: injectors, 22 of 374 complaints (5.9%) against a 1.2% median.
Duramax LML: the CP4.2 high-pressure fuel pump, 83 of 779 complaints (11%) against a 0.3% median.
Duramax LML: the DPF / DEF system, 33 of 779 complaints (4.2%) against a 0.1% median.
Duramax L5P: the DPF / DEF / NOx sensors, 72 of 1,229 complaints (5.9%) against a 0.1% median.

The trucks

Half-ton? F-150: 2.7 vs 3.5 EcoBoost vs 5.0.

Complaints: NHTSA owner complaints filed under the truck's 2500/3500 (F-250/F-350) names, all years filed, one per complaint number. Engine: decoded from the complaint's VIN (position 8 is the engine code) with NHTSA's vPIC decoder. Complaints filed as just “Silverado” or “Sierra” are left out (they mix 1500s and HDs). Older trucks have had more years to collect complaints, and popular years draw more because more were sold. Source: NHTSA owner complaints (FLAT_CMPL + COMPLAINTS_RECEIVED_2025-2026), received through 20261109; NHTSA vPIC VIN decoder; NHTSA recalls API.

Quick answers

Which diesel truck engine has the most engine complaints?

By VIN-matched owner complaints, the Ford 6.0 Power Stroke: 34% of its complaints name the engine. A share, not a failure rate.

Which diesel truck engine has the fewest engine complaints?

The Cummins 5.9 (Ram): 4% of its complaints name the engine.

Diesel truck engines compared.