The Power of Diesel: Why the Cummins Engine is the Heart of RAM Heavy Duty

More than 70 percent of RAM Heavy Duty customers choose diesel power for good reason. The 2025 6.7-litre Cummins High-Output Turbo Diesel engine represents the latest evolution of a proven design, producing 430 horsepower and 1,075 lb-ft of torque. These numbers tell only part of the story – it's how this engine builds and manages that power that makes it ideal for serious work applications.

Working closely with Cummins engineers, RAM has refined this inline-6 diesel to improve drivability, fuel economy, durability, and serviceability while increasing power output. The result is an engine that handles Quebec's demanding winter conditions and heavy workloads with equal confidence.

Engineering Excellence: Built for Heavy-Duty Work

The Cummins 6.7-litre uses a compacted graphite iron block with cast-iron heads – materials chosen specifically for durability under high-stress conditions. The 16.2:1 compression ratio extracts maximum energy from each drop of diesel fuel, while the electronic high-pressure common rail injection system provides precise fuel metering across all operating conditions.

Key technical specifications:

• Displacement: 6,690 cubic centimetres
• Configuration: Inline-6 cylinder, turbocharged and intercooled
• Peak Power: 430 hp at 2,800 rpm
• Peak Torque: 1,075 lb-ft at 1,800 rpm
• Compression Ratio: 16.2:1

The pushrod-operated overhead valve system with 24 valves and hydraulic lifters reduces complexity while maintaining precise valve timing. This design proves more durable than overhead cam systems in dusty or demanding work environments.

The turbocharger and intercooler work together to force cool, dense air into the cylinders. More air allows complete combustion of larger fuel quantities, creating the torque output that makes heavy towing possible.

Torque Delivery: Power When You Need It

Peak torque arrives at just 1,800 rpm and remains available through 2,800 rpm – exactly where diesel engines work most efficiently. This broad torque band means the engine doesn't need high rpm to generate pulling power, reducing stress on internal components and improving fuel economy.

This torque curve matches perfectly with the TorqueFlite HD eight-speed transmission. The transmission's wide gear ratios keep the engine operating in its most efficient range, whether you're accelerating from a construction site or maintaining highway speeds with heavy trailers.

The 3.42:1 rear axle ratio works with this torque output to provide 16,606 kg of maximum towing capacity – a 70 percent increase in torque delivery compared to the previous generation 2500.

Construction and Durability Features

The redesigned block includes robust heavy-duty pistons and connecting rods engineered for sustained high-load operation. Larger intake and exhaust valves improve port flow, while the new performance intake manifold optimizes air distribution to all six cylinders.

The higher-pressure fuel system operates at increased injection pressures, creating finer fuel atomization for more complete combustion. This improves both power output and emissions compliance while reducing fuel consumption.

For serviceability, the engine uses top-feed injectors and top-load lubrication systems. Integrated fuel filters simplify maintenance, while improved intake port geometry provides better access for service work.

Cold weather operation in Quebec winters benefits from standard glow plugs that warm the combustion chambers for reliable starting in extreme temperatures. The engine maintains full power output even in sub-zero conditions.

Transmission Integration and Performance

The TorqueFlite HD eight-speed automatic transmission includes specific calibrations for diesel operation. The transmission recognizes loaded versus unloaded conditions and adjusts shift patterns accordingly.

When the system detects trailer weight, it holds lower gears longer to keep the engine in its torque band. This prevents the constant gear hunting that occurs when transmissions try to chase fuel economy with insufficient power.

The wide ratio spread allows the more efficient 3.42:1 rear axle ratio while maintaining low-speed pulling capability. Previously, maximum towing required a 4.10 axle ratio that increased fuel consumption at highway speeds.

Electronic Range Select mode gives drivers manual control over gear selection during challenging conditions like boat launches or construction site maneuvering.

Fuel Economy and Efficiency

Despite increased power output, the new Cummins engine improves fuel economy compared to previous generations. The higher-pressure injection system, improved combustion chamber design, and optimized turbocharger all contribute to better efficiency.

The engine management system continuously monitors operating conditions and adjusts fuel injection timing, quantity, and pressure to optimize performance. During light-load highway cruising, the system prioritizes efficiency. Under heavy acceleration or towing loads, it focuses on power delivery.

Selective Catalytic Reduction (SCR) emission controls use diesel exhaust fluid to reduce nitrogen oxide emissions while maintaining engine efficiency. The system operates transparently without affecting performance or fuel economy.

Noise, Vibration, and Harshness Improvements

Diesel engines traditionally produce more noise and vibration than gasoline engines. The 2025 Cummins addresses these concerns through several engineering improvements.

Helical transmission gears reduce gear noise and vibration compared to straight-cut gears. The improved engine mounting system isolates vibration from the cab structure. Sound-deadening materials in the engine bay reduce diesel clatter that reaches the passenger compartment.

The inline-6 configuration provides inherent balance that V-8 diesels cannot match. This reduces vibration and contributes to smoother operation at all engine speeds.

Maintenance and Service Life

Commercial-grade construction means extended service intervals and longer component life. Engine oil capacity reaches 11.3 litres, providing thermal mass to manage heat generated during sustained high-load operation.

The cooling system holds 22.5 litres of coolant – significantly more than gasoline engines. This capacity maintains stable operating temperatures during extended towing or high ambient temperatures.

Recommended maintenance intervals:

• Engine oil changes every 15,000 km for normal duty
• Fuel filter replacement every 30,000 km
• Air filter inspection every 20,000 km
• Coolant system service every 150,000 km

The engine management system monitors operating conditions and adjusts service reminders based on actual usage patterns. Severe-duty operation triggers earlier service intervals to protect engine components.

Real-World Applications

The Cummins diesel's capabilities extend beyond towing capacity numbers. Construction companies use these trucks for daily equipment transport, maintaining full power output even after hours of operation. Farmers rely on the sustained torque for field work and harvest-season demands.

The combination of 1,075 lb-ft torque and 16,606 kg towing capacity handles virtually any equipment trailer, large RV, or commercial application. The engine maintains this capability while meeting current emission standards and providing competitive fuel economy.

For businesses that depend on their trucks for daily operation, the Cummins diesel provides the reliability and durability that minimize downtime and maximize productivity.

The 2025 Cummins High-Output Turbo Diesel proves that advanced engineering can improve performance, efficiency, and durability simultaneously. Experience the torque and reliability of a Cummins. Schedule a test drive in a RAM Heavy Duty truck at our Montreal-Est dealership.