Ram 2500 6.7 Cummins Specs: Towing, MPG & Reliability 2026

The am 2500 6.7L Cummins Turbo Diesel specs have grown from 350 HP and 650 lb-ft of torque at its 2007.5 debut to 430 HP and 1,075 lb-ft in 2026 — a climb that spans four distinct generations and five transmission options. Knowing which year and which output variant you have matters for towing, tuning, and buying decisions.

The engine your Ram 2500 actually came with depends on model year, transmission pairing, and whether it is Standard Output or High Output. Below is the complete breakdown by generation, starting with the specs that matter most.

6.7L Cummins Horsepower and Torque by Year (2007 to 2025)

The 6.7L Cummins Turbo Diesel has gone through four distinct output generations since its 2007.5 debut in the Ram 2500 and 3500. Each generation brought real torque and horsepower gains, driven largely by transmission upgrades, ECU calibration improvements, and fuel system changes.

The table below covers every model year, showing Standard Output (SO) and High Output (HO) figures where both applied. Note that the HO engine was exclusive to the Ram 3500 from 2013 through 2024. Ram 2500 trucks ran the SO engine throughout that period. For 2025, Ram standardized the HO engine across both the 2500 and 3500, as confirmed by Cummins at the 2025 launch.

⚠️ 2019–2020 trucks are subject to NHTSA Recall 21V880 (CP4 fuel pump replacement). Check your VIN at nhtsa.gov if you own one of these trucks.

Those are the headline numbers. Now look at the core engine specs that stay consistent across all years — and where they changed.

6.7L Cummins Engine Specs That Stay the Same Across All Years

The 6.7L Cummins Turbo Diesel is an inline-6 diesel displacing 408 cubic inches, with an architecture that has stayed largely intact since its 2007.5 debut. The specs below apply to all pickup truck variants unless noted.

• Displacement: 408 cu. in. (6,690cc)
• Configuration: Inline-6 cylinder (I-6), liquid-cooled, turbocharged, intercooled
• Bore x Stroke: 4.21 in. x 4.88 in. (107mm x 124mm)
• Valvetrain: OHV, 24 valves (4 per cylinder)
• Compression Ratio: 17.3:1 on SO engines; 16.2:1 on HO engines (2019+) — the lower HO ratio enables higher boost pressure without detonation
• Firing Order: 1-5-3-6-2-4
• Block Material: Grey cast iron (2007–2018); Compacted Graphite Iron / CGI (2019–2024 HO); grey cast iron again (2025)
• Oil Capacity: 12 qt (11.3L) with filter
• Coolant Capacity: 29.5 qt (28.0L)
• Fuel Requirement: Ultra Low Sulfur Diesel (ULSD) only
• Turbocharger: Holset HE351VE VGT (2007–2012); Holset HE300VG VGT (2013+)

For a visual breakdown of how these components fit together under the hood, the 6.7 Cummins engine diagram and component guide maps every major system with labeled callouts.

The fuel system is where the biggest changes happened between generations — and those changes have real implications for reliability and ownership cost.

6.7L Cummins Fuel System and Emissions Changes by Generation

The fuel system evolution is the most important spec for anyone buying a used Ram 2500 or 3500. It determines reliability, repair costs, and tuning headroom more than any other single factor.

Gen 3 (2007.5 to 2012) — Bosch CP3 Pump

The original 6.7L Cummins launched with a Bosch CP3 high-pressure common rail pump rated at 26,000 psi and a Holset HE351VE Variable Geometry Turbocharger (VGT). The VGT also provided exhaust brake functionality, which was new for the segment.

Emissions hardware from day one included a DPF (Diesel Particulate Filter) and EGR (Exhaust Gas Recirculation) system. No DEF (Diesel Exhaust Fluid) was required on pickups through 2012 — a NOx absorption catalyst handled nitrogen oxide reduction instead. This is the reason Gen 3 trucks are popular with tuners: fewer emissions system variables and a proven CP3 pump.

Gen 4 (2013 to 2018) — CP3 With SCR and DEF Added

The 2013 model year brought two significant changes. First, SCR (Selective Catalytic Reduction) became standard on all pickup trucks, requiring DEF to be injected into the exhaust stream on every tank fill. Second, a new High Output variant debuted exclusively on the Ram 3500, paired with the Aisin AS69RC 6-speed automatic.

The CP3 pump carried through all of Gen 4. A new Holset HE300VG turbocharger replaced the HE351VE. Power and torque climbed steadily — the HO engine hit 930 lb-ft by 2018 — driven primarily by ECU calibration improvements rather than major hardware changes. The G56 6-speed manual was available through 2018 but was significantly de-rated, making just 660 lb-ft even as the 68RFE-equipped SO trucks produced 800 lb-ft.

Gen 5 (2019 to 2020) — CP4 Era and Recall 21V880

The 2019 model year brought the most comprehensive 6.7L redesign since launch. Cummins fitted a new Bosch CP4.2 high-pressure fuel pump capable of 29,000 psi, a CGI block on HO engines, hydraulic lifters, a revised cylinder head, and updated turbocharger calibration. The HO engine crossed 1,000 lb-ft for the first time. The G56 manual was discontinued.

The CP4.2 pump proved problematic. Its internal roller tappets require more fuel lubricity than Ultra Low Sulfur Diesel in North America provides. Premature failures sent metal debris through the entire fuel system, requiring repairs that could exceed $10,000 in severe cases.

Stellantis issued NHTSA Recall 21V880 in November 2021, covering approximately 222,410 Ram 2500, 3500, 4500, and 5500 trucks built for the 2019 and 2020 model years. The recall replaced the CP4.2 with a CP3 unit at no cost. Owners of 2019–2020 Ram HD trucks should verify their VIN status at nhtsa.gov if the recall has not yet been completed.

If you are researching which 6.7L years to avoid for a used truck purchase, our 6.7 Cummins years to avoid guide covers the Gen 3, Gen 4, and Gen 5 reliability breakdown in detail.

2021 to 2024 — CP3 Restored, HO Torque Climbs

Cummins reverted to the Bosch CP3 pump for all 2021 model year engines before the 21V880 recall was formally issued. The HO engine received a new ECU calibration that added 20 HP and 75 lb-ft, reaching 420 HP and 1,075 lb-ft. SO engines stayed at 370 HP and 850 lb-ft. This 2021–2024 generation is the most recent proven platform before the 2025 redesign.

2025 and Beyond — Bosch CP8, ZF 8-Speed, HO Only

The 2025 model year represents the biggest single-generation change in the 6.7L’s history. Cummins fitted an all-new Bosch CP8 injection pump rated at 32,000 psi. A ZF TorqueFlite HD 8-speed automatic replaced both the 68RFE and Aisin 6-speeds. Glow plugs replaced the grid heater for improved cold-start emissions. A new bolt-on aluminum intake manifold with longer runners replaced the integrated design.

Critically for Ram 2500 buyers: Ram standardized the HO engine across all 2025 pickup models. The SO engine was discontinued. For the first time, a Ram 2500 diesel buyer gets 430 HP and 1,075 lb-ft straight from the factory, as announced by Cummins at launch.

With the fuel system understood by generation, the transmission pairing is the next spec that changes what your Cummins actually makes at the wheels.

Which Transmission Pairs With the 6.7L Cummins in Each Ram Generation

The transmission your Ram HD came with determines how much torque the 6.7L Cummins is calibrated to produce. Two trucks from the same model year can have different torque ratings based solely on their gearboxes. Here is the full pairing history.

Chrysler 68RFE 6-speed automatic (2007.5–2024): The standard transmission in Ram 2500 trucks throughout Gen 3, Gen 4, and Gen 5. All SO engine torque figures in the table above apply to 68RFE-equipped trucks.

Mercedes G56 6-speed manual (2007.5–2018): Available as a no-cost option through the 2018 model year. Required a significantly de-rated engine calibration. In 2018, G56 trucks produced just 660 lb-ft versus the 68RFE’s 800 lb-ft and the Aisin’s 930 lb-ft on the HO engine. The G56 was not offered for 2019 or later.

Aisin AS69RC 6-speed automatic (2013–2024, Ram 3500 and chassis cabs): Introduced with the HO engine in 2013. Stronger case and higher torque capacity than the 68RFE, which is why HO output was possible only with this gearbox. Not available in Ram 2500 pickups.

ZF TorqueFlite HD 8-speed automatic (2025+): Standard on all 2025 Ram 2500 and 3500 pickups. Replaces both the 68RFE and the Aisin. The 8-speed’s closer gear ratios improve towing grade performance and reduce highway cruise RPM. It is the only transmission offered for 2025.

Standard Output or High Output — that question matters most if you are comparing a Ram 2500 to a Ram 3500. Here is exactly what the difference means.

6.7L Cummins Standard Output vs High Output — What Changes

For Ram 2500 buyers, the Standard Output 6.7L Cummins was the only diesel option from 2007.5 through 2024. The High Output engine was reserved for Ram 3500 trucks during that entire period. The difference between the two goes deeper than the output numbers.

Standard Output (SO) — Ram 2500 application, 2007.5 to 2024:

• 370 HP / 850 lb-ft (Gen 5, 2019–2024)
• Paired with Chrysler 68RFE 6-speed automatic
• Grey cast iron block throughout all SO years
• 19.0:1 compression ratio (Gen 5)

High Output (HO) — Ram 3500 application, 2013 to 2024:

• 420 HP / 1,075 lb-ft (2021–2024 peak)
• Paired with Aisin AS69RC 6-speed automatic
• Compacted Graphite Iron (CGI) block (2019–2024) for higher cylinder pressure tolerance
• 16.2:1 compression ratio — lower than SO, which allows more boost pressure without detonation risk

The lower HO compression ratio is a deliberate engineering trade. By reducing static compression, Cummins gave the turbocharger room to pile on more boost pressure without triggering knock. The result is higher effective cylinder pressure at full load and more torque, handled safely by the CGI block’s superior strength.

For 2025, Ram standardized the HO engine on the Ram 2500 for the first time. Every 2025 Ram 2500 diesel buyer gets 430 HP, 1,075 lb-ft, and the ZF 8-speed as standard equipment. If you are evaluating towing capacity by configuration, the Ram 2500 towing capacity guide covers the full year-by-year ratings with configuration breakdowns.

If the SO or HO specs have you thinking about what upgrades are worth doing on your existing Cummins, our breakdown of the best 6.7 Cummins upgrades covers the performance mods that deliver real gains without breaking reliability.

What the 6.7L Cummins Specs Mean for Your Ram 2500

The Ram 2500 6.7L Cummins Turbo Diesel is one of the most spec-tracked engines in the diesel truck segment for good reason. From 350 HP in 2007.5 to 430 HP in 2025, the engine has improved every generation without losing the low-end torque that makes it the benchmark for heavy towing.

For used truck buyers, the clearest guidance is this: 2007.5–2012 trucks offer simplicity without DEF and a proven CP3 pump. The 2013–2018 generation added DEF but kept the CP3 and delivered steady torque gains. The 2019–2020 trucks carry CP4 risk — verify recall 21V880 is completed before purchase.

The 2021–2024 generation is the most refined pre-redesign Cummins available. And 2025 marks the first year a Ram 2500 buyer gets HO power as the base offering.

Use the specs table above as your reference before any purchase, tuning session, or parts order. Every torque figure, fuel pump, and transmission pairing is generation-specific — and getting those details right is what separates a confident diesel decision from an expensive guess.

6.7L Cummins Specs Questions Ram 2500 Owners Ask Most

How much horsepower does a stock 6.7 Cummins have in a Ram 2500?

It depends on the model year. Ram 2500 trucks from 2007.5 through 2012 produced 350 HP. From 2013 through 2024, the Ram 2500 ran the Standard Output engine at 370 HP. Starting with the 2025 model year, Ram standardized the High Output engine at 430 HP across both the 2500 and 3500.

What is the oil capacity of a 6.7 Cummins?

The 6.7L Cummins holds 12 quarts (11.3 liters) of engine oil including the filter. This figure applies across all Ram pickup truck applications from 2007.5 through 2024. Always use oil meeting Cummins CES 20081 / API CK-4 specification, with 10W-30 recommended above 0°F and 5W-40 synthetic below 0°F.

What transmission does the Ram 2500 6.7 Cummins use?

Ram 2500 trucks used the Chrysler 68RFE 6-speed automatic from 2007.5 through 2024. The G56 6-speed manual was an option from 2007.5 through 2018. For 2025, all Ram 2500 diesel trucks use the ZF TorqueFlite HD 8-speed automatic exclusively.

Is the 6.7 Cummins Standard Output or High Output in a Ram 2500?

Standard Output through 2024. The HO engine was reserved for Ram 3500 trucks from 2013 through 2024. Starting with the 2025 model year, the Ram 2500 receives the High Output 6.7L Cummins as standard equipment — the first time the HO engine has been offered in a three-quarter-ton Ram truck.

What year did Ram change the 6.7 Cummins to High Output only?

2025. That model year, Ram discontinued the Standard Output engine and standardized the HO 6.7L Cummins — paired with the new ZF 8-speed transmission — across all Ram 2500 and 3500 diesel trucks. The SO engine rated at 370 HP and 850 lb-ft is no longer available from the factory.