What 2500 diesel gets the best MPG?

Among current 3/4-ton pickups, the Ram 2500 with the 6.7-liter Cummins diesel typically delivers the best highway mpg, especially in a 2WD setup with the right axle ratio. Real-world results vary with payload, terrain, and model year.

Diesel-powered 2500s emphasize torque and towing capability more than pure efficiency, but modern transmissions and engine tuning have narrowed the gap between brands. This report compares the main 2500 diesel options and explains how to maximize fuel economy in each configuration.

Top diesel 2500 contenders and their efficiency potential

Here's a quick look at the primary 2500 diesel pickups in the current market and what analysts say about their highway efficiency in typical use.

• Ram 2500 with 6.7-liter Cummins Turbo Diesel — widely considered the most efficient of the bunch on highway driving, especially in 2WD with the larger rear-axle ratio; typical highway mileage trends into the low-to-mid 20s mpg, with lower figures under heavy payload or towing.


• Ford F-250 Super Duty with 6.7-liter Power Stroke — strong torque and a refined 10-speed automatic; highway mpg generally in the low 20s depending on configuration, with city mpg lower and towing reducing efficiency further.


• Chevrolet Silverado 2500HD / GMC Sierra 2500HD with Duramax 6.6-liter — capable workhorses with competitive powertrain reliability; highway mpg commonly in the high teens to low 20s depending on drivetrain and payload, with 4x4 variants usually lower than 2x4.

All three families offer diesel options that balance heavy-duty tasks with usable highway efficiency, but numbers shift with year, cab/bed configuration, axle ratio, and whether the truck is 4x4 or 2x4.

Tips to maximize MPG in a 2500 diesel

Practical steps you can take before and during ownership to squeeze more miles out of each gallon:

• Choose the 2WD configuration when you don’t need 4x4 for weather or off-road work; it typically delivers better highway efficiency.


• Select an axle ratio appropriate for highway driving, such as 3.42 or 3.73, which can improve cruise efficiency when towing or hauling light loads.


• Maintain proper tire pressure and weight; underinflated tires and extra ballast increase rolling resistance and hurt mpg.


• Keep engine and fuel systems well maintained; clean air filters and a well-tuned engine help efficiency.


• Use cruise control on highways and plan routes to minimize stops and idling; avoid aggressive acceleration and heavy throttle while cruising.


• Limit rooftop cargo and accessories that increase aerodynamic drag; remove unnecessary weight from the bed when not towing.


• When towing, use the correct towing mode and consider trailer gear ratios designed for efficiency, and be mindful that towing will reduce mpg.

Adopting these practices can lead to noticeable gains in highway fuel economy while preserving the trucks’ essential capabilities.

Note on numbers and updates

Exact mpg numbers vary by model year, cab/bed configuration, drivetrain, and payload. For the most accurate, configuration-specific ratings, consult the official EPA estimates on fueleconomy.gov or the automaker’s window sticker for your chosen build.

Summary: For buyers prioritizing mpg in a 2500 diesel, the Ram 2500 with the 6.7L Cummins is typically the best option in highway efficiency, but the Ford F-250 and GM Duramax variants remain close contenders depending on configuration. Always verify the EPA numbers for your exact build and test-drive to gauge real-world fuel economy.

What mpg does a 6.7 Cummins get?

The 6.7L Cummins engine typically gets 15–18 mpg for mixed city/highway driving and 17–21 mpg on the highway when unloaded. However, fuel economy varies significantly based on the vehicle model, year, and driving conditions, with towing and city driving resulting in lower mileage. For instance, a user reported getting 9-12 mpg while towing. 
Typical mileage

• Mixed driving: ~15–18 mpg
• Highway (unloaded): ~17–21 mpg 

Factors that affect mileage

• Towing: Towing heavy loads drastically reduces mileage. For example, a user reported getting 9-12 mpg while towing a small car and around 10-12 mpg towing 12,000 lbs. 
• Driving conditions: City driving, especially with frequent stops and starts, will result in lower fuel economy compared to highway cruising. 
• Vehicle and model year: Newer models may have slightly different fuel economy ratings. For example, some users report highway mileage in the 19-21 mpg range for newer models. 
• Modifications: Aftermarket parts, like higher-flowing air intakes, can potentially improve fuel economy. 
• Maintenance and driving habits: Regular maintenance and smooth driving habits, like steady speeds and avoiding rapid acceleration, can also help improve mileage. 

How to estimate your mileage

• Use the provided ranges as a general guide. 
• Keep in mind that your actual mileage will depend on the specifics of your vehicle and how and where you drive it. 
• Monitor your own fuel economy over time to get the most accurate picture for your specific situation. 

What is the gas mileage on a 6.7 PowerStroke vs 6.7 Cummins?

The Ford 6.7L Powerstroke generally gets better highway mileage, typically between 19–20 MPG when unloaded, while the 6.7L Cummins averages around 16–18 MPG. However, the Cummins often performs better under heavy towing loads due to its high low-end torque. Real-world fuel economy can vary significantly depending on factors like model year, vehicle condition, payload, and driving habits. 
This video compares the performance of a 6.7L Powerstroke and a 6.7L Cummins in a pulling competition: 57sMann Family FarmsYouTube · Jul 3, 2021
6.7L Cummins

• Highway MPG (unloaded): 16–18 MPG
• City MPG: Around 12 MPG
• Towing: Stronger under heavy towing loads due to high low-end torque. 

This video shows a MPG challenge comparing a 6.7L Duramax, 6.7L Cummins, and a 6.7L Powerstroke: 56sThe Fast Lane TruckYouTube · Jun 19, 2018
6.7L Powerstroke

• Highway MPG (unloaded): Up to 20 MPG
• City MPG: Around 14–15 MPG
• Towing: Often slightly less fuel-efficient when towing heavy loads compared to the Cummins. 

Key considerations

• Load: The 6.7L Powerstroke tends to have an advantage in fuel economy when unloaded, but this gap narrows significantly or reverses when towing heavy loads, where the Cummins' torque becomes a benefit. 
• Model Year: Fuel economy can vary between different model years for both engines due to design updates. 
• Driving Conditions: Urban vs. highway driving, speed, and driving habits will all affect the final MPG. 
• Towing/Payload: When a truck is fully loaded, fuel economy drops for both engines. Some drivers report a full load can bring the MPG down to around 11.2 MPG for either engine, though this is highly variable. 

What fuel mileage does a 6.6 l Duramax diesel get?

The 6.6L Duramax engine's MPG varies, but typically ranges from 15-18 MPG for mixed driving and 17-20 MPG for unloaded highway driving. Actual mileage depends heavily on factors like driving conditions, towing, and the specific model year. Some newer models achieve higher efficiency, with a 2025 Silverado HD hitting 20.4 MPG on a controlled highway loop. 
This video shows a fuel economy test of a 2021 Chevy Silverado HD with the 6.6L Duramax engine towing a trailer: 48struckguyjoeYouTube · Jan 15, 2021
Mileage breakdown by driving type: 
This video demonstrates a fuel economy test of a 2024 Chevy Silverado HD Duramax: 57sDaily MotorYouTube · Jun 27, 2023

• Mixed/City: Around 15 MPG or lower, especially with stop-and-go traffic. 
• Highway (unloaded): Typically 17-20 MPG, but can vary with speed. 
• Towing: Expect significantly lower mileage, often in the 10-14 MPG range depending on the load and terrain. 

Factors that influence MPG:

• Towing and load: Hauling heavy loads reduces fuel efficiency. 
• Driving conditions: Hilly terrain or stop-and-go city traffic lowers MPG. 
• Vehicle age and break-in: Newer trucks may improve after an initial break-in period, with some owners reporting increased mileage after a few thousand miles. 
• Other factors: Speed, road conditions, and factors like the truck's emissions system (e.g., temporary DPF regen cycles) can also have an effect. 

You can watch this video to see real-world mileage results for a 2022 GMC Sierra 2500 Duramax: 1mDaily MotorYouTube · Mar 26, 2022

What is the best mpg for a 2500 diesel truck?

In that world, the frontrunners are the Chevrolet/GMC 2500 Duramax (6.6L), Ford F-250 Power Stroke (6.7L), and Ram 2500 Cummins (6.7L). Unloaded highway results often sit in the 17–20 mpg window, with mixed driving around 15–18 mpg.