6.7 Cummins Engine: Everything You Need to Know

One of the most talked-about 6.7L diesel engines on the road today is the 6.7 Cummins.

The 6.7 Cummins offers strong power from 350 to 420 horsepower and up to 1,075 lb-ft torque. It shines in towing and lasts over 300,000 miles with care. Upgrades boost it to 1,200 horsepower safely.

Individuals purchase these trucks to pull, move, and drag tough miles. Over the years, the engine changed; new emissions gear, stronger parts, and more power.

This ultimate guide covers everything you need to know about the 6.7 Cummins engine, including the specs, reliability, common problems, maintenance tips, upgrades, and essential maintenance tips for maximum reliability and power. Follow the guide below and unlock the full potential of your 6.7 Cummins.

6.7 Cummins Engine Overview and Generations

The 6.7L Cummins is an extension of the previous Cummins inline-6 models. It is more updated and has a balance between power and emissions.

This is a robust player in the Dodge/Ram heavy-duty trucks, having been used in that model. The most significant 6.7 Cummins generations and their changes are briefly listed below.

The 6.7 Cummins has three main generations from 2007 to now. Early years focus on simplicity. Later ones add power and emissions tech. Best balance is 2013-2018 for tuning and strength.

6.7 Cummins Generations Breakdown

• 2007–2012 (Pre-DEF)— This era is simpler. The engine uses a CP3-style fueling system and fewer aftertreatment parts. It's the easiest for tuning and mechanical work. These models are often called the best for basic, mechanical reliability and aftermarket support. Many owners like their straightforwardness for modifications.
• 2013–2018 (Early DEF)— Diesel Exhaust Fluid (DEF) and Selective Catalytic Reduction (SCR) systems arrived to meet emissions rules. Hardware was updated, transmissions got stronger in many trucks, and fuel system parts were improved. These years strike a strong balance between tunability and emissions hardware — a common pick for buyers.
• 2019–Present (High Output)— The High Output (HO) versions pushed stock torque toward 1,000 lb-ft in some trims. Turbo design and fueling revisions followed, and later models commonly feature the CP4.2 high-pressure pump in certain years. (Notably in 2019-2022 Ram trucks before the return to the CP3 in some recent models). These trucks are powerful from the factory but add some new failure points to watch.

Engine Info

• 6.7 Cummins Oil Capacity

Product Reviews

• Best 6.7 Cummins Delete Kit
• 6.7 Cummins DPF Delete Pros & Cons
• What Happens if Not Changing the 6.7 Cummins CCV Filter

Many owners point to 2013–2018 as the sweet spot: decent emissions tech but still friendly to tuners and generally robust in service life.

6.7l Cummins Engine Specs by Year

Below is a compact table showing peak stock numbers and a major change for reference. These are representative factory numbers and common platform details.

Specs vary by year. 2007 models give 350 horsepower and 650 lb-ft. By 2019, High Output reaches 400 horsepower and 1,000 lb-ft. 2025 boosts to 420 horsepower and 1,075 lb-ft in HO versions.  

Year	HP (stock)	Torque (stock)	Major Change
2007	350	650 lb-ft	First-gen 6.7 introduced; simpler fueling (CP3 era)
2013	385	850 lb-ft	DEF / SCR systems added (early DEF era)
2019+	400	1,000 lb-ft	High Output variants; revised turbo & fueling, Aisin AS69RC available

Note: 1,000 lb-ft torque figure is for High-Output models paired with the Aisin transmission.

Source: Compiled from publicly available Ram Truck specifications.

The table indicates how the 6.7 Cummins engine has developed over the years. It is not a mere engine as it used to be, but a modern high-torque diesel.

6.7 Cummins Reliability & Common Problems

It is a great option, though it does have disadvantages. The cost and severity of each of the issues are different.

Top issues include CP4 pump failure, EGR cooler leaks, turbo problems, and DEF clogs. Fixes range from $600 to $4,000. Prevention like additives helps a lot.  

This table will examine some of the general problems of the Cummins 6.7L turbo diesel engine and possible solutions to them.

Problem	Symptoms	Typical Fix Cost	Prevention
CP4 Pump Failure	Metal in fuel, sudden no-start, low pressure	$4,000+ (pump + rails + injectors)	Install a lift pump, run lubricity additives, and monitor the fuel system
EGR Cooler Leaks	White smoke, coolant loss, overheating	$600–$1,200	Replace with an upgraded cooler, or use an off-road EGR delete where legal
Turbocharger Issues	Boost lag, abnormal whistle, low power	$800–$1,500	Periodic cleaning, check the actuator, fresh oil, and filters
DEF System Clogs / SCR Issues	Reduced power derate, codes, limp mode	$300–$1,000	Use quality DEF, keep the DEF tank clean, and follow service intervals

Pro Tip: For later engines, using the correct oil spec is vital. Models 2019+ in particular benefit from low-ash CK-4 oils to help avoid DPF and aftertreatment problems.

Notes: The costs are approximate and can vary based on labor rates and using OEM vs. aftermarket parts.

Common Failure Patterns Explained in Plain Terms

• CP4 vs CP3: Some later 6.7s moved to the CP4.2 high-pressure fuel pump. When a CP4 fails, it can send metal into the fuel rail and ruin injectors, a very expensive cascade. Prevent this with a good lift pump and fuel cleanliness. Many tuners recommend a CP3 swap when pushing high power.
• EGR and DPF issues: In our experience, using a dedicated EGR cleaner every other oil change and ensuring the truck completes active regenerations can help clear out carbon buildup.
• Turbo wear: Vane turbos and variable geometry designs need periodic attention. Boost leaks or actuator faults show up as loss of power and increased smoke.

6.7 Cummins Performance Mods & Power Potential

Power gains should be planned in steps. Each step must balance performance with reliability. The most common path is: improve fueling, improve airflow, then increase boost. Fueling and cooling are the foundations; neglect them, and other upgrades fail faster.

Stages go from stock 350-420 horsepower to built engines over 1,200. Deletes add 100+ horsepower. Turbos push to 800. Costs start at $0 and hit $15K.  

Clear staging gives predictable results.

Stage 1 — Mild (Tune + Basic Supporting Mods)

An economical and low-risk solution is to make use of a custom ECU tune, a cold-air intake, and upgrade the exhaust. While the gains won't be significant, they will definitely be noticeable.

They help with throttle response and towing performance while keeping the stock horsepower 6.7 Cummins close to safe limits. Expect roughly +80–120 HP at the wheels, depending on the truck and tune.

Stage 2 — Moderate (Fueling + Turbo)

Add a quality lift pump, larger injectors, or a CP3 conversion, and a single larger turbo. This stage unlocks solid mid-range power and peak gains. The resulting RWHP is around 450-650 with much higher torque as well.

With these changes, your Cummins 6.7L turbo diesel will pull harder; however, driveline limits (transmission and torque converter) need evaluation.

Stage 3 — Serious (Compound Turbos + Built Fuel System)

Compound turbos, dual CP3s, or an upgraded high-pressure system, and stronger drivetrain components are required here. This stage supports 700–1,200 RWHP on builds that include forged internals and upgraded cooling. Fuel delivery and oil cooling become mission-critical.

Stage 4 — Race/Drag (Full Rebuild)

Forged pistons, ARP head studs, performance heads, and a race-level fuel system are required for 800+ RWHP. This is a dedicated race or off-road setup, not suitable for daily street trucks unless every supporting system is upgraded.

Fuel System Considerations First

A failing high-pressure pump can ruin injectors and rails. For many high-power builds, the order of upgrades should be: lift pump (to ensure clean, high-volume fuel supply to the high-pressure pump) → fueling upgrade (CP3 swap or dual CP3s) → turbo & tune.

This protects parts and avoids costly failures associated with the CP4 pump in some later trucks.

Driveline and Transmission Limits Matter

For higher torques, transmissions need to be upgraded. For example, For example, the popular but often overstressed 68RFE transmission starts slipping at around 500 lb-ft.

An upgraded transmission can help with the extra load. Nevertheless, when there is additional power, it is worth checking your torque converters, clutches and axles.

Real-world Example to Set Expectations.

As an example, a 2010s truck with an S363 turbo, CP3 swap, and a normal tune will put in the 600-650 RWHP and over 1200 lb-ft on a chassis dyno. However, to achieve this level, it is worthwhile to have an upgraded fuel system, transmission, and cooling initially.

Safety Margins and Sustainable Power

Short bursts of high power can be achieved with aggressive tuning, but sustained loads reveal weak points. Pistons and connecting rods are the final limiting factor on the engine. For builds targeting sustained high horsepower, forged internals and optimized oil pressure are non-negotiable.

If you are going to upgrade your 6.7 L Cummins turbo diesel engine, you would also require preventive upgrades. This will help the engine run for longer without any issues.

6.7 Cummins Maintenance Schedule (By Mileage)

Below are some ways to check and care for your engine according to a proper schedule to prevent any future problems.

Every 5,000 miles: Oil and filter change. Every 15,000: Fuel filter. Every 50,000: Coolant flush. Follow this for long life.  

Every 5,000 miles

• Replace engine oil with a full-synthetic CK-4 formula (e.g., 5W-40).
• Change oil filter (e.g., Fleetguard LF3972).
• Rapid turbo actuator test; ensure no odd sounds.

Every 15,000 miles

• Replace the fuel filter.
• Inspect transmission fluid.

Every 50,000 miles

• Coolant flush.
• EGR valve and cooler inspection/cleaning.
• Inspect DPF system — cleaning if regeneration is failing.

Other Important Milestones

• CP4 watch: Many CP4 pumps begin to present risk near 150K miles. Consider a preventative CP3 conversion kit or add a high-capacity lift pump if you want more tuning or extra miles.
• Transmission service: Your truck's transmission also plays an important role. As an example, in 68RFE vs Aisin AS69RC, the 68RFE is likely to slip once the torque reaches and exceeds 500lb-ft. This implies that the heavy towing or power mods may require upgrading of the transmission.

Best 6.7 Cummins Upgrades for Longevity & Power

There are times of sacrificing some of the performance to have a long-lasting product and vice versa. However, with the right knowledge, it is possible to make easier selections of upgrades.

Budget mods like lift pumps cost $500-1,000. They prevent failures. High-end like compound turbos add power for $3,000+.  

Must-Do Budget Mods ($500–$1,000)

• FASS or DieselTek lift pump can help reduce stress for the high-pressure pump.
• BD or OEM EGR cooler upgrade can help reduce heat soak and reduce EGR failures.
• Cold air intake (S&B, K&N style)allows for better airflow and cleaner intake.

BD or OEM EGR cooler upgrade can help reduce heat soak and directly address the EGR cooler leaks discussed in the Common Problems section.

Note: Mention of specific brands is for illustrative purposes based on their reputation within the Cummins community; other quality brands are available.

High-End Performance ($3,000+)

• Compound turbo setups(e.g., S362 + S480): big power gains with good spool and top end.
• Hamilton Cams valve springs/head work: needed for higher RPM and boost reliability.
• 100+ HP injectors + dual CP3s: required for sustained high horsepower builds.

Fuel system strategy

• For safe tuning: lift the pump first, then the CP3 conversion if you exceed ~600 HP. This saves money and prevents diesel system failures.

Longevity upgrades are worth the spend

• Strong head studs (ARP) and a quality head gasket if running sustained high boost.
• Upgraded oil cooler and thermostat; keep EGTs and oil temps controlled.

These upgrades let you scale power while protecting the engine. Treat fueling and cooling as foundational; they fail before forged pistons do.

6.7 Cummins Delete Kit and Emissions (with Legal Disclaimer)

Delete kits remove EGR, DPF, DEF. Gain power. But federally illegal. Fines up to $10,000. Use off-road only.  

There is demand for EGR/DPF delete kits because they simplify the engine, reduce soot buildup, and unlock power.

It is critical to understand that deleting emissions equipment for on-road use is a federal offense in the U.S. and many other countries, carrying the risk of substantial fines.

Penalties and fines may be high, and erasing systems will nullify factory warranties. Always follow local laws. Consider emissions-compliant performance options or use delete hardware for off-road or race vehicles only, in regions where that is legal.

Practical Alternatives

• Use high-quality emissions-friendly tunes that recover performance without permanently removing hardware.
• Consider maintenance and hardware upgrades that reduce soot and extend component life without deleting parts.

If you decide to pursue a delete for off-road use only, insist on pro installation and plan for separate legal street-use solutions.

Dyno Data: Real-World 6.7 Cummins Power Gains (Proven by Testing)

Dyno numbers tell the real story: what your truck is actually putting down to the wheels, not just what's advertised.

Stock: 320-400 wheel horsepower. Deletes add 120. Turbos push 550-800. Safe limits: 450 on CP4, 500 on trans.  

Here's a look at what you can expect in terms of real-world power, common upgrade results, and where the safe limits are before parts start to give out.

1) Stock 6.7 Cummins Power (At the Wheels)

Based on aggregated dyno results from community builds and tuner data, a stock 2007-2012 model typically puts down.

• 2007–2012 (CP3 Era): Around 320–350 WHP and 600–650 lb-ft of torque.
• 2013–2018 (Early DEF Era): Typically 340–380 WHP and 750–850 lb-ft.
• 2019+ High Output Models: About 370–400 WHP and 850–950 lb-ft.

These are the numbers you'd see from a healthy, stock truck on a chassis dyno, not factory “flywheel” ratings.

2) Most Common Upgrades & Their Gains

• Delete + Tune: Roughly +120 HP at the wheels, depending on the tune and truck setup.
• Single Turbo (S364.5SXE): Expect 550–600 WHP, provided fueling upgrades are in place.
• Compound Setup (S362 + S480): With the right fuel system and internal engine work, 800+ WHP is achievable.

Each upgrade has its pros and cons; tuning adds quick power, single turbos bring a stronger midrange punch, and compounds are for those chasing serious numbers.

3) Safe Limits Before Breaking Parts

Any additional horsepower puts additional strain on your truck parts; hence, it is best to observe where the boundaries lie to prevent one part from dropping.

• Fuel Pump (CP4): The CP4 stock is very weak at heavy loads above 450 WHP and is reported to have early failures. A large number of the owners upgrade to a CP3 conversion or install a lift pump to be reliable.
• Transmission (68RFE): The 68RFE factory cannot take up much more than 500 lb-ft of torque before it begins to slip. A built transmission or improved torque converter is necessary in case you intend to tune or to tow heavy.
• Engine Internals: At about 650 WHP, the stock rods and pistons begin to reach their limit. In addition to this, you will require forged internals and better components of the driveline to ensure reliability.
• Stock Head Bolts: Factory head bolts can lift the head under high boost above ~550-600 WHP, making ARP head studs a critical upgrade.

Practical Takeaway

Most 6.7 Cummins builds (daily driven, tow-capable engine) are sweet from 500-600 WHP. This level allows the truck to be so strong without having to worry if any part will break.

To stay reliable, make sure to upgrade the fuel system, transmission, and tuning. And if you're going beyond that, plan for forged internals and a fully built driveline.

Cummins 5.9 vs Cummins 6.7: Comparison

5.9 is reliable and simple. 6.7 adds power but emissions. 5.9 gets better mpg. 6.7 tows more.  

A simple comparison is provided below to assist buyers when they need to decide between the older 5.9 and the modern 6.7.

Feature	Cummins 5.9	Cummins 6.7
Era	Older, simple	Modern, higher output
Common HP (stock)	235–400 (varied)	350–400 (stock HO)
Torque	460–800 lb-ft (varies)	650–1,000 lb-ft
Emissions	Simpler carb/emissions setups (pre-2007.5 models had no DPF)	DEF, DPF, EGR systems
Tunability	Very tune-friendly, simpler	Tunable but more complex (aftertreatment)
Fuel pump types	Mostly the CP3 era on the later 5.9s	CP3/CP4 introduction, depending on the year
Ease of repair	Easier on some older models	More complex in later models
Suitability for builds	Excellent for budget builds	Better for high torque and modern truck platforms

Both engines have fans. The 5.9 is loved for simplicity. The 6.7 gives more torque and modern refinements but needs careful attention to emissions and fueling.

FAQs

Q1: What's the safest HP for a stock 6.7 Cummins?

A: Aim for 500–550 WHP as the upper safe range on a stock bottom end and stock fueling. Beyond this, head studs, forged pistons, and a fuel system upgrade become necessary.

Q2: Can you delete a 6.7 Cummins legally?

A: No, for on-road use in many countries. It is federally illegal in the U.S. and will likely void warranties. You can use it off-road only if the local law allows for it.

Q3: How often should I change my Cummins fuel filter?

A: Preferably, it must be after every 15,000 miles. But in case you have lower quality fuel, then it is good to test it after every 10,000 miles.

Q4: What's the best oil for a 6.7 Cummins?

A: Rotella T6 5W-40 (CES 20081 / CK-4 compliant). AMSOIL Signature lines are also solid choices.

Q5: What's better — CP3 swap or lift pump for fuel reliability?

A: Both have their place. Start with a lift pump (prevents CP4 stress). If you need more than 600 HP or better fueling reliability for high load, you may want to consider a CP3 swap. For ultimate peace of mind, especially on 2019-2022 models, the CP3 swap is the definitive solution.

Q6: Will a 6.7 Cummins last 500K miles?

A: Yes, it can last 500K miles if you provide it with regular maintenance, clean fuel, proper oil, and aftertreatment. Avoid repeated CP4 failures and control EGTs.

Final Thoughts: Is the 6.7 Cummins a Good Engine?

The 6.7 Cummins delivers power and durability. Follow this guide for best results.  

The 6.7 Cummins engine sits between two worlds: modern emissions tech and old-school diesel toughness. It wakes early with torque, and it keeps working when cared for. Pick the model year to match intent; simpler mechanicals for older rigs, better factory torque for recent high-output Cummins 6.7 trucks.

Maintenance pays dividends. Clean fuel, CES 20081 / CK-4 oil, timely filters, and cooling checks prevent most nasty failures. The fuel system is the engine's nervous system; protect it first.

A modest lift pump changes risk profiles more than some expensive toys. Later trucks with the CP4 pump need particular attention; a fueling strategy prevents expensive chain-reaction failures.

Performance should be built in stages. Start with airflow and fueling, then add boost. Transmission and driveline limits arrive sooner than engine internals in many builds.

The 68RFE and stock torque converters often become the weak link, not the block. For high-power ambitions, plan for forged internals, head studs, and an upgraded fuel train.

Emissions gear complicates choices. Legal on-road compliance matters. Deals bring power but also legal and warranty costs. Emissions-friendly tunes and hardware upgrades are a quieter, safer path for daily drivers.

Is the 6.7 cummins a good engine? Yes, ultimately, the 6.7 Cummins rewards a proactive, informed owner. Focus on foundational health—fueling and cooling—before chasing peak power, and this engine will be a capable and long-lasting partner.

About the Author- John Barrett

More Reading

• About RAM Cummins
• 6.7 Cummins Engine Oil
• Optimizing Cummins 6.7L Diesel Performance