Ram 3500 High-Output Diesel: Real-World Fuel Economy & Towing Performance

The Ram 3500 with the high-output Cummins diesel engine represents the pinnacle of heavy-duty truck capability, delivering an impressive 400 horsepower and earth-moving 1,000 lb-ft of torque. But how does this translate to real-world fuel efficiency when pushed to its limits? MotorVero conducted rigorous testing to reveal the true cost of unmatched towing capacity.

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Engineering Behind the High-Output Cummins Diesel

While maintaining the proven 6.7-liter displacement, Ram engineers made significant improvements to the Cummins turbo-diesel for the high-output configuration:

Weight Reduction Without Sacrificing Strength

The engine block now utilizes compacted graphite iron (CGI), saving 60 pounds compared to traditional cast iron while maintaining exceptional durability. This advanced material offers superior strength-to-weight ratio, crucial for handling the tremendous cylinder pressures generated by the high-output tuning.

Comprehensive Internal Upgrades

Nearly every internal component received enhancements to handle the increased power:

• Redesigned cylinder head with improved flow characteristics
• High-strength valves and upgraded valve springs
• Reinforced rocker arms and pivot assemblies
• Forged steel connecting rods with larger bearings
• Revised piston design for better combustion efficiency
• High-flow exhaust manifold and turbocharger upgrades

Drivetrain Reinforcements

To properly harness the increased output, Ram strengthened multiple drivetrain components:

• Heavy-duty Aisin AS69RC automatic transmission with enhanced cooling
• Reinforced frame rails with additional crossmembers
• Upgraded axle shafts and wheel bearings
• High-capacity braking system
• Dual rear wheels for improved load distribution
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Testing Methodology: Real-World Fuel Economy Evaluation

MotorVero conducted controlled testing in Utah to evaluate the Ram 3500's fuel efficiency under different load conditions. Our 62.3-mile route included:

• Steep mountain grades (4,500 to 5,400 ft elevation changes)
• Interstate highway sections (65-75 mph)
• Rural two-lane roads (45-55 mph)
• Urban stop-and-go traffic
• Twisting mountain roads (25-35 mph)

Test Vehicle Specifications

Our Ram 3500 Limited 4×4 test truck featured:

• Crew cab/long bed/dual rear wheel configuration
• High-Output Cummins diesel ($11,795 option)
• Max Tow Package (4.10 axle ratio, rear air suspension)
• Fifth Wheel/Gooseneck Towing Prep Group
• Transfer case skid plate and tonneau cover
• Luxury interior with 12-inch Uconnect system
• As-tested price: $87,810

Payload and Towing Capacity Verification

According to the doorjamb sticker, our specific truck had:

• Payload capacity: 4,818 lbs
• Maximum towing: 30,800 lbs (15% tongue weight)
• GCWR: 25,182 lbs
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Fuel Economy Results: Empty vs. Maximum Load

We conducted two complete test loops under different conditions:

Unladen Performance (Driver Only)

• Calculated fuel economy: 13.8 mpg
• Onboard computer reading: 15.1 mpg (9% optimistic)
• Fuel consumed: 4.52 gallons
• Average speed: 41.4 mph

Towing 16,000-Pound Equipment Trailer

• Calculated fuel economy: 9.5 mpg
• Onboard computer reading: 9.9 mpg (4% optimistic)
• Fuel consumed: 6.58 gallons
• Average speed: 38.7 mph
• Tongue weight: 1,600 lbs (using weight-distribution hitch)
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Comparative Analysis: How the Ram 3500 Stacks Up

When examining these results, several important comparisons emerge:

Against Previous Generation

Our earlier testing of a single-rear-wheel Ram 3500 with the standard-output Cummins and 3.42 axle ratio showed:

• 16.9 mpg empty (vs. 13.8 mpg for high-output)
• 9.9 mpg towing (nearly identical despite lower power)

Class Competitors

While direct comparisons are challenging due to different test conditions, industry data suggests:

• Ford Super Duty 6.7L Power Stroke: 14-15 mpg empty, 8-9 mpg towing heavy
• Chevrolet Silverado 3500 Duramax: 13-14 mpg empty, 8-9 mpg towing heavy
• All three trucks show similar efficiency when working hard
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Ownership Considerations: When the High-Output Diesel Makes Sense

The Ram 3500 High-Output Cummins excels in specific use cases:

Best Applications

• Regular towing above 20,000 lbs
• Fifth-wheel or gooseneck trailer users
• Commercial operators needing maximum capability
• Heavy equipment transporters
• Those prioritizing power reserve over fuel economy

Potential Drawbacks

• Significant fuel cost increase over SRW models
• Reduced maneuverability in urban areas
• Higher initial purchase price
• Commercial license requirements for max towing
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Technical Deep Dive: Why the High-Output Gets Lower MPG

Several factors contribute to the Ram 3500's fuel consumption characteristics:

Drivetrain Losses

The 4.10 axle ratio provides tremendous mechanical advantage for towing but increases engine RPM during cruising. This is particularly noticeable when unloaded, where the engine operates further from its optimal efficiency range.

Aerodynamic Impact

The dual rear wheel configuration creates additional drag due to:

• Increased frontal area
• Turbulence between dual tires
• Wider track requiring extended fender flares

Weight Penalty

The high-output package adds considerable mass:

• Heavier engine components
• Reinforced drivetrain parts
• Additional cooling capacity
• Dual rear wheel assembly
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Real-World Driving Impressions

Beyond the numbers, the Ram 3500 High-Output delivers an exceptional driving experience:

Unloaded Behavior

• Noticeable turbo lag at low RPM due to large turbocharger
• Firm ride quality from stiff suspension tuning
• Confident braking feel despite massive weight

Towing Performance

• Effortless acceleration even on steep grades
• Excellent exhaust brake modulation
• Stable tracking at highway speeds
• Minimal trailer sway with proper load distribution

Cost of Ownership Analysis

Prospective buyers should consider these financial factors:

Fuel Cost Projections

Based on 15,000 annual miles (30% towing):

• Annual fuel cost: ~$3,900 (at $3.50/gallon diesel)
• Compared to SRW model: ~$750/year additional
• Compared to gasoline HD: ~$1,200/year savings

Resale Value Considerations

• High-output models command ~10-15% premium used
• Diesel engines typically outlast gasoline counterparts
• Commercial buyers value max capability units
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Final Verdict: Who Should Choose the Ram 3500 High-Output?

The Ram 3500 with the high-output Cummins diesel makes no apologies for its thirst when unloaded - because that's not what it was designed for. This truck exists to move massive loads with confidence and control, offering:

• Class-leading towing stability
• Unmatched power reserves
• Premium interior accommodations
• Engineering overkill for severe duty cycles

For operators who regularly tow above 20,000 pounds or demand absolute maximum capability, the fuel economy tradeoffs become justified. However, for those whose needs fall below 15,000-pound towing, a single-rear-wheel configuration with the standard-output diesel likely offers better overall value.