The 6.7L Cummins Turbo Diesel (B6.7) is one of the most legendary heavy-duty diesel engines used in Ram 2500, Ram 3500, and commercial trucks. Known for its extreme torque output, long lifespan, and towing capability, it is widely used in both personal and industrial applications.
Built by Cummins, this inline-6 turbo diesel engine is designed for durability under heavy loads, long-distance driving, and commercial hauling. Proper oil maintenance is the key factor in achieving 300,000–500,000+ miles of service life.
This guide covers full engine specifications, oil type, oil capacity, fuel economy, maintenance cost, service intervals, and common issues.
6.7 Cummins Engine Overview
The Cummins B6.7 engine has been used in Ram heavy-duty trucks since 2007 and continues to evolve with improved emissions systems, fuel efficiency, and durability upgrades.
It is an inline-6 turbocharged diesel engine designed for high torque at low RPM, making it ideal for towing heavy trailers, construction work, and long-haul driving.
Key Insight: The 6.7 Cummins produces up to ~1,075 lb-ft torque in modern high-output versions, making it one of the strongest diesel engines in the pickup segment.
Engine Specifications
Fuel Economy (MPG)
- City: 12–16 MPG
- Highway: 18–24 MPG
- Combined: 14–20 MPG
6.7 Cummins Engine Oil Type
Using the correct oil is extremely important for diesel longevity, turbo protection, and injector system health.
In colder climates, 5W-40 synthetic oil is preferred for easier cold starts. For heavy towing and hot climates, 15W-40 remains widely used.
Oil Capacity
- Standard Capacity: ~12 quarts (with oil filter)
- Cab & chassis versions may vary slightly
- Always verify final level using dipstick
Oil Change Interval
- Normal driving: 7,500–10,000 miles
- Heavy towing: 5,000–7,500 miles
- Severe duty: 3,000–5,000 miles
Oil Change Cost
- DIY: $80 – $140
- Local shop: $120 – $180
- Dealer service: $180 – $300
Common Problems
- EGR soot buildup in intake system
- Turbo wear in high-mileage engines
- CCV filter clogging
- Injector wear under heavy duty cycles
- Occasional oil leaks at seals and gaskets
Maintenance Tips
- Use CK-4 rated diesel engine oil only
- Replace oil filter every oil change
- Check oil every 1,000–2,000 miles
- Service fuel filters regularly
- Monitor turbo and air intake system
Frequently Asked Questions (FAQ)
What oil does a 6.7 Cummins take?
Most models use 15W-40 or 5W-40 full synthetic diesel engine oil meeting CK-4 specification.
How much oil does a 6.7 Cummins hold?
It holds approximately 12 quarts including oil filter change.
How often should oil be changed?
Every 7,500–10,000 miles under normal use, or sooner under heavy towing conditions.
Is the 6.7 Cummins reliable?
Yes, it is considered one of the most durable diesel engines when properly maintained.
Final Thoughts
The Cummins 6.7L diesel engine is a proven workhorse designed for extreme durability and torque output. With proper oil maintenance, regular servicing, and correct driving habits, it can easily deliver long-term reliability for both commercial and personal use.
- Engine: 6.7L Inline-6 Diesel
- Power: 370–420 HP
- Torque: 850–1075 lb-ft
- Oil Type: 15W-40 / 5W-40 CK-4
- Oil Capacity: ~12 Quarts
- Oil Change: 5,000–10,000 miles