The major heavy-duty diesel engines powering current Class 8 trucks, with their real horsepower and torque ranges — the same engines this site's Fault Code Lookup tool covers diagnostically.
Detroit (Daimler Truck)
Detroit's mainstream long-haul engine, standard in most Freightliner Cascadias — the most common engine on the road in North America by sheer Cascadia volume.
Displacement
14.8L, inline-6
Horsepower
425–505 hp (Gen 5); 425–505 hp with more torque on Gen 6
Torque
1,550–1,850 lb-ft (Gen 5); 1,650–1,900 lb-ft (Gen 6)
The smaller DD13 (370–525 hp) is Detroit's other Cascadia option — lighter weight for better payload, at the cost of some low-end torque compared to the DD15.
PACCAR
PACCAR's engine for both the Peterbilt 579 and Kenworth T680 — the same engine, badged for both brands.
Displacement
12.9L, inline-6
Horsepower
405–510 hp
Torque
1,450–1,850 lb-ft
A CARB-compliant variant is offered at 455 hp/1,650 lb-ft or 510 hp/1,850 lb-ft specifically for California operation.
Cummins
Cummins' flagship heavy-duty engine, available across multiple OEM chassis (including as an option in the Freightliner Cascadia) — the widest-availability engine of any brand since it isn't tied to one truck maker.
Displacement
14.9L, inline-6
Horsepower
336–605 hp depending on series (Efficiency: 400–500 hp; Performance: 485–565 hp; Productivity: 430–605 hp)
Torque
1,450–2,050 lb-ft depending on series
Weight
~3,166 lb
Cummins sells the X15 in three tuned series (Efficiency, Performance, Productivity) for the same base engine — the right one depends on whether you're optimizing for fuel economy, pulling power, or heavy-haul duty cycle.
Volvo
Volvo's only engine offering in the VNL, available in standard variable-geometry turbo or turbo-compound configurations.
Horsepower
405–455 hp
Torque
1,450–1,850 lb-ft
The turbo-compound version recovers extra energy from exhaust gas to boost efficiency — it's the version paired with the higher torque ratings.
Mack
Mack's mainstream on-highway engine for the Anthem, also offered in the fuel-efficiency-focused MP8HE variant.
Displacement
12.8L (783 ci), inline-6, overhead cam
Horsepower
434–505 hp (standard MP8); 415–445 hp (MP8HE)
Torque
1,460–1,760 lb-ft (standard); 1,760–1,860 lb-ft (MP8HE)
The MP8HE trades some peak horsepower for turbo-compounding — Mack's own literature markets it around a 3% fuel efficiency gain over the standard MP8.
International (Navistar)
International's engine, sold exclusively as part of the S13 Integrated Powertrain rather than as a standalone engine option — it isn't offered separately from the T14 transmission.
Displacement
13L, inline-6
Horsepower
Up to 515 hp
Torque
Up to 1,850 lb-ft
Weight class
Lightest 13-liter diesel currently sold in North America
Because it's sold as an integrated unit with the T14 transmission, you can't mix an S13 with a different transmission brand the way you sometimes can with other OEM engines.
The Cummins X15, in its Productivity series tune, tops out at 605 hp — the highest of the mainstream Class 8 engines. But peak horsepower isn't the only factor that matters; torque curve and how it's tuned for your duty cycle usually matters more for real-world fuel economy and drivability.
The DD15 is the larger-displacement engine (14.8L vs. the DD13's smaller displacement) with a higher torque ceiling, while the DD13 is lighter — which can mean more payload capacity. Which one makes sense depends on whether you're prioritizing pulling power or weight savings for your freight.
PACCAR (Peterbilt and Kenworth's parent company) primarily specs its own MX-13 engine, though Cummins engines have historically been available as an option on some PACCAR trucks depending on model year and configuration — check current factory order options for your specific model year rather than assuming based on an older truck.
Specs reflect common current factory options and can change by model year or region — always confirm exact figures against the manufacturer's current build sheet before making a purchase or maintenance decision.