This guide gives shoppers and owners a clear, real-world view of highway mpg for heavy-duty 2500-series pickups. Car and Driver’s 75-mph tests found diesel models averaged about 18 mpg, while gas models averaged roughly 15 mpg — a noticeable gap but not a guarantee for every model.
These are work-focused trucks built for towing and payload. Expect durability and capability first; fuel efficiency is relative. Only two diesels hit 20 mpg in tests: a 2018 Ram 2500 and a 2023 Ford F-250 Super Duty.
This article compares diesel vs gas, and Ford vs Ram vs GM within the 2500 class. It explains how configuration, load, terrain, and speed change the best mpg. You’ll get a highway benchmark, model-by-model takeaways, and a cost vs mpg section to help decide if a diesel option makes sense.
Key Takeaways
- Diesel models generally show better highway mpg in real tests.
- Average tested gap: about 18 mpg (diesel) vs 15 mpg (gas).
- Not every diesel reaches 20 mpg; configuration matters.
- Decide based on typical use: commuting or heavy towing.
- See a practical look at range and reserves with a real-world range test: real-world range.
How Fuel Economy Is Measured for Heavy-Duty ¾-Ton Trucks in the U.S.
Real-world highway miles matter more than sticker claims. Many heavy duty pickups are exempt from EPA mpg labels because their gross vehicle weight rating (GVWR) tops 8,500 pounds. That leaves buyers without apples-to-apples EPA numbers for these vehicles.
So how do testers fill the gap? Car and Driver runs a repeatable 200-mile out-and-back loop on I-94 at a 75-mph target. That steady interstate pace shows how the powertrain actually burns fuel on long runs.
Why many ¾-ton HD trucks don’t publish EPA mpg (GVWR exemption)
When a vehicle’s GVWR is over 8,500 lbs, manufacturers often don’t have to publish EPA mpg. Shoppers must rely on independent tests or manufacturer guidance instead of a standard sticker.
What a real-world 75-mph highway test shows drivers more clearly than estimates
- Consistent route and speed produce comparable mpg numbers across model years.
- Tests highlight real fuel burn under steady conditions, not ideal lab cycles.
- Trim, tires, bed length, and added equipment still change results within the same model year.
| Measure | What it shows | Why it matters |
|---|---|---|
| GVWR exemption | No EPA mpg required | Shoppers need independent numbers for fair comparison |
| 75-mph loop | Real-world highway mpg | Reflects steady interstate driving habits |
| Test consistency | Repeatable results | Improves value when comparing vehicles and years |
| Configuration variance | Different trims and gearings | Explains within-model mpg spread |
We use these numbers as a benchmark—not a guarantee. Later sections will explain diesel vs gas, standard vs high-output engines, and why a tested base may differ from a buyer’s chosen build.
¾ Ton Diesel Truck Fuel Economy Comparison Using Real-World Highway MPG Data
Real-world 75-mph runs reveal how heavy-duty pickups behave on long interstate stints. Car and Driver’s loop shows a clear gap: diesel models averaged about 18 mpg while gas models averaged roughly 15 mpg.
That ~3 mpg difference equals roughly a 20% advantage for diesel powertrains. Most diesels cluster between 16 and 19 mpg, so modest gains add up on long drives.
Only two entries hit 20 mpg: a 2018 Ram 2500 and a 2023 Ford F-250 Super Duty. These standouts matter for buyers who log highway miles regularly.
- Expectations: diesels typically return 16–19 mpg; gas entries fall toward the lower end.
- Distribution: tested trucks ranged from 14 to 20 mpg, so single mpg shifts are meaningful.
- Low results: the worst numbers come from gas-calibrated HD models set for towing and torque.
This pattern sets up the next, model-by-model analysis of Ford, Ram, and GM entries and shows how configuration and year change highway mileage.
| MPG | Count | Example |
|---|---|---|
| 14 | 3 | 2020 F-350 (gas) |
| 18 | 3 | Average diesel group |
| 20 | 2 | 2018 Ram 2500, 2023 Ford F-250 |
Ford F-250 Super Duty vs Ram 2500 vs Silverado 2500HD vs Sierra 2500HD
Four flagship 2500-series nameplates show where real-world highway mpg lands when fitted with their common diesel engines. Below are concise takeaways for each model and why those highway numbers matter alongside towing and capability.
Ford F-250 Super Duty with 6.7L High-Output Power Stroke: mpg takeaway and why it matters
The f-250 super duty High-Output Power Stroke hit 20 mpg in a 75-mph test. That result stands out because most diesels in this class cluster 16–19 mpg.
Why it matters: the high-output tuning pairs strong power and low-rpm torque with efficient cruising. For buyers who haul big trailers often, the extra towing capability can come with surprisingly good highway fuel efficiency.
Ram 2500 with 6.7L Cummins diesel: mpg takeaway and what “standard vs high-output” changes
The ram 2500 has a history of strong highway numbers; a 2018 Cummins reached 20 mpg in testing. Standard-output and high-output tunings change torque curves, which can alter mpg depending on gearing and load.
In plain terms, high-output gives more torque and often better trailer control, while standard-output can be slightly more frugal when lightly loaded.
Chevrolet Silverado 2500HD with 6.6L Duramax diesel: mpg takeaway and how it compares in the real world
The silverado 2500 equipped with the 6.6L duramax diesel has posted real-world runs near 19 mpg. Those results place GM’s diesel near the top tier on long interstate runs.
Trim, tires, and bed choices can move that number up or down, so build matters.
GMC Sierra 2500HD with 6.6L Duramax diesel: mpg expectations and where it typically lands
The Sierra mirrors the Silverado mechanically, so expect similar highway mpg. Equipment and aerodynamic differences can shift results, but a well-specced Duramax Sierra commonly lands in the high-teens on steady highway runs.
| Model | Engine | Real-world highway result |
|---|---|---|
| Ford F-250 Super Duty | 6.7L High-Output Power Stroke | ~20 mpg |
| Ram 2500 | 6.7L Cummins | ~20 mpg (select test years) |
| Silverado 2500HD | 6.6L Duramax | ~19 mpg |
| GMC Sierra 2500HD | 6.6L Duramax | High-teens mpg |
Bottom line: base models in buyer guides are often gas engines, but the best highway fuel efficiency in this class usually comes with diesel options that balance torque, towing, and steady cruising performance.
Diesel vs Gas Powertrains in ¾-Ton Trucks: Efficiency, Torque, and Usability
Choosing the right powertrain depends on how you use the vehicle. Real-world 75-mph tests show diesel models average about 18 mpg versus roughly 15 mpg for gas, a near 20% edge in steady interstate work.
Why diesel often wins at highway cruising: diesel engines make high torque at low rpm, so they hold speed with less throttle and fewer downshifts. That reduces transient fuel burn when towing or carrying heavy loads.
Gas V8s bring quick throttle response and lower upfront cost. But, they run higher rpm on grades and during accelerations, which raises fuel use and often places gas models near the lower end of tested mileage.
Transmission gearing and axle ratios change the outcome a lot. Modern multi-speed automatics can let two trucks with the same engine return different results based on final drive, tire size, and calibration.
| Factor | Typical effect | Why it matters |
|---|---|---|
| Low-rpm torque | Improves steady mpg | Fewer high-rpm events when towing |
| Axle ratio / gearing | Shifts highway rpm | Alters real-world mileage |
| Transmission steps | Smooth cruising | Reduces throttle demand on long runs |
Practical takeaway: pick diesel for frequent long towing and heavy loads. Choose gas if you want lower purchase cost and simpler service for lighter duty or shorter ownership cycles.
What Changes MPG the Most: Configuration, Weight, and Driving Conditions
How a vehicle is set up and how it’s driven often outweighs the engine when it comes to highway mileage. Car and Driver’s test fleet were all automatics and 4WD, yet bed lengths, body styles, tires, and trim lists produced measurable differences on the 200-mile 75-mph loop.
4WD, tires, and trims: why the “same” truck returns different highway mileage
Drivetrain components, tire size, and heavy trim packages add rolling resistance and extra weight. That combination lowers mpg even with the same powertrain. Smaller, low-rolling-resistance tires and lighter trim help fuel efficiency on long drives.
Body style and bed length effects
Cab configuration and bed length change aerodynamics and curb weight. A crew cab with a long bed often costs a few tenths of mpg versus a regular cab. Those small shifts add up over highway miles.
Payload, trailer weight, and aerodynamic drag
Payload and trailer loads force the engine to work harder. Aerodynamic drag grows rapidly at interstate speeds, so a heavy trailer or rooftop gear can slash mileage. In short, added weight and drag are the hidden killers of fuel efficiency.
Speed and route: why the 75-mph benchmark matters
At 75 mph, wind resistance dominates and gearing shows itself. That’s why the 200-mile loop is a useful baseline: it reflects real U.S. interstate driving and gives a repeatable way to compare base highway performance before towing or hauling.
| Factor | Typical effect | Why it matters |
|---|---|---|
| 4WD / drivetrain | Higher rolling losses | Lower highway mpg |
| Body style / bed | Changes aero & weight | Shifts steady-mileage |
| Payload / trailer | Increased load | Reduces fuel efficiency |
Towing and Real-World Loads: What MPG Looks Like When You’re Working
Towing changes mpg more than you expect; numbers from unloaded highway runs are only a baseline. When you add a trailer, route, and weather, average mileage can fall sharply.
Why unloaded highway mpg doesn’t predict towing mpg
Baseline tests show steady cruise efficiency, but they omit trailer shape, weight, and sustained grades. Those factors drive consumption more than the engine alone.
Real-world example
A 2012 Chevrolet 2500 4×4 with the 6.0 gas V8 pulled a motorcycle trailer (about 500 lb) for 1,900 miles and averaged ~11 mpg.
Speeds ranged from 65–75 mph; mountain passes pushed the engine to roughly 4,000 rpm and cut economy hard.
How grades and rpm impact fuel burn
- Higher rpm on climbs multiplies consumption—sustained 4,000 rpm segments dominated the trip average.
- Diesel vs gas: diesels hold speed with fewer high-rpm events, but heavy loads, wind, and speed can erase gains.
- Plan conservatively: estimate tow mpg lower than base highway numbers and focus on capacity and control.
| Condition | Typical effect | Why it matters |
|---|---|---|
| Steep grade | RPM spike (~4,000) | Large mpg drop |
| Headwind | Higher drag | Worse mileage |
| Trailer shape | Increased aero loss | Lower average mpg |
Cost vs MPG: Does Paying Extra for a Diesel Engine Pencil Out?
Calculating whether an upgraded engine pays off requires a clear miles-and-cost comparison. Use a realistic highway case and simple math to see if a price premium is justified.
Fuel savings math over time
Example: Car and Driver compared a 2017 gas model to a 2018 diesel model. Over 50,000 miles, the diesel saved ~625 gallons.
If diesel saves 625 gallons, multiply by your assumed fuel price to find total savings. Then divide the diesel premium by that savings to get years or miles-to-payback.
Upfront price and option stacking
Diesel options, tow packages, and higher trims raise the purchase price and push the break-even point further out. Account for every option when calculating payback.
Choosing by job and ownership context
If you tow often and rack high annual miles, the diesel path usually makes sense. For occasional towing and lower miles, a gas engine often has a faster financial case.
| Factor | Typical effect | Why it matters | Notes |
|---|---|---|---|
| Gallons saved (50k miles) | ~625 | Drives dollar savings | Based on Car and Driver example |
| Upfront premium | $3,000–$10,000 | Changes payback miles | Includes engine and common options |
| Maintenance & emissions | Higher complexity | Affects total ownership cost | Consider service intervals and parts |
| Resale value | Often higher for diesel | Offsets some purchase cost | Depends on market and year |
Bottom line: mpg matters, but true value depends on miles, job type, and option choices. Run the math with your local prices and annual miles to pick the smartest powertrain for your work.
Conclusion
Steady interstate runs reveal how configuration and use change real mpg more than badges do.
Bottom line: in real 75-mph testing, diesel models averaged about 18 mpg versus roughly 15 mpg for gas. Only two diesel entries reached 20 mpg in tests: the 2018 Ram 2500 and the 2023 Ford F-250 Super Duty.
Use that base as a benchmark. Expect many diesels in the 16–19 mpg band and gas engines to sit lower on similar highway runs. Torque delivery, powertrain calibration, gearing, and how you use the vehicle—unloaded commuting versus towing a trailer—change mileage far more than a badge. Pick the engine and options that match your towing needs, annual miles, and ownership time horizon, and treat highway mpg as a starting point to set real expectations for performance and capacity.
FAQ
How is fuel economy measured for ¾‑ton heavy‑duty trucks in the U.S.?
The EPA tests lab-based city and highway cycles for light vehicles, but many ¾‑ton heavy‑duty trucks fall under GVWR exemptions and don’t receive official EPA mpg labels. Independent testers run real‑world highway drives—often at 75 mph with typical loads—to show usable mpg under interstate conditions. That combination of lab and real‑world data gives the best picture of on-road efficiency.
Why don’t many ¾‑ton HD pickups publish EPA mpg figures?
Trucks with a gross vehicle weight rating above certain thresholds are exempt from EPA labeling rules. Manufacturers can still provide estimates, but those figures aren’t standardized. As a result, buyers rely on manufacturer specs for fuel consumption, independent road tests, and fleet reports for realistic mpg numbers.
What does a 75‑mph highway test reveal compared with manufacturer estimates?
A 75‑mph test shows highway rolling resistance, aerodynamic losses, and transmission behavior at sustained high speed. It usually produces lower mpg than conservative manufacturer figures, but it represents typical U.S. interstate driving. The test highlights differences between engines, gearing, and aero treatments that matter for long hauls and towing.
How much better are diesel powertrains vs gasoline in real‑world highway mpg for these trucks?
On highway runs, modern diesels commonly return about 15–25% better mpg than comparable gasoline V8s, mainly because of higher thermal efficiency and stronger low‑end torque. Exact gains depend on configuration, weight, and speed, but a 20% advantage is a reasonable rule of thumb for many ¾‑ton rigs under steady cruising.
What is the typical highway mpg range for HD pickups at interstate speeds?
Expect a broad range: efficient diesel‑equipped ¾‑ton models often sit in the high teens to around 20+ mpg on level highway runs. Gasoline variants commonly range from the low to mid‑teens. Configurations, 4×4 systems, tires, and payload can move those numbers up or down several mpg.
Which ¾‑ton models regularly hit about 20 mpg on the highway?
The standouts are usually diesel‑powered, long‑geared, lightly loaded crew‑cab models with aerodynamic packages. Examples include well‑spec’d Ford Super Duty and GM HD trucks with Duramax or Power Stroke diesels when driven at steady interstate speeds and without heavy towing.
What do the lowest highway mpg results tell us about gas HD trucks?
The lowest numbers reflect high‑drag setups, tall, heavy trims, 4×4 drivetrains, short bed/aero penalties, or high‑rpm climbing. Gas V8s typically suffer more under heavy loads and steep grades, which pushes mpg down compared to diesels during demanding duty cycles.
How does the Ford F‑250 Super Duty 6.7L High‑Output Power Stroke perform in mpg terms?
The 6.7L High‑Output Power Stroke focuses on torque and towing capability. In real‑world highway tests it often posts competitive mpg for its class, especially when paired with tall axle ratios and careful gearing. Its strength is holding speed under load while keeping rpm—and therefore fuel burn—lower than many gas alternatives.
What mpg differences should I expect between standard and high‑output Cummins in the Ram 2500?
The standard 6.7L Cummins balances efficiency and capability; the high‑output unit prioritizes torque and towing. Real‑world mpg can drop slightly with the high‑output tune, mainly under light loads where extra fuel is used to support higher torque capability. Under heavy towing, the high‑output version may narrow the gap or even improve overall fuel use by staying in lower rpm bands.
How does the Chevy Silverado 2500HD 6.6L Duramax compare in real driving?
The 6.6L Duramax is competitive on highway mpg, especially with tall gearing and aerodynamic aids. In practice it often matches or slightly trails the most efficient Power Stroke setups but leads many gasoline V8s. Consistency under load and strong low‑end torque make it efficient for sustained towing.
What mpg should I expect from the GMC Sierra 2500HD with the 6.6L Duramax?
The Sierra 2500HD’s real‑world mpg mirrors the Silverado when configured similarly. Differences come down to axle ratios, wheel/tire choices, and trim weight. With the right setup, expect highway figures in the high teens to about 20 mpg in light‑load conditions.
How does torque and low‑rpm power affect real‑world efficiency when hauling or towing?
High low‑end torque reduces the need to downshift or climb rpm under load, which lowers fuel consumption during acceleration and on grades. Diesel powertrains typically deliver this torque at lower rpm, improving efficiency for towing and heavy payload work compared with higher‑revving gasoline engines.
When does a gas V8 still make sense despite worse mpg?
Gas V8s make sense for buyers who prioritize lower upfront cost, lighter curb weight, or who rarely tow heavy loads. They offer lower maintenance costs in some cases and quicker warm‑ups in cold climates. For occasional towing and everyday driving with lighter payloads, gasoline engines can be the better financial fit.
How do transmissions and final drive gearing change highway mpg?
Transmission gear counts, lock‑up behavior, and final drive ratios determine cruising rpm at highway speeds. More gears and a transmission that locks the torque converter help keep rpm low, improving mpg. Tall axle ratios can reduce rpm at 75 mph, but too tall a ratio can hurt performance when towing hills.
How much do 4WD, tires, and trim choices affect highway mileage?
Switching from 2WD to 4WD, fitting aggressive all‑terrain tires, or choosing heavier trims can reduce highway mpg by several percent. Rolling resistance, added drivetrain drag, and extra weight are the main culprits. Even identical model names can return different mpg because of these options.
Do cab style and bed length change fuel consumption?
Yes. Crew cabs add weight and slightly increase frontal area, while long beds can affect weight distribution and aerodynamics. Generally, a shorter bed or regular cab may be a bit more efficient, but real‑world differences are modest compared with drivetrain and towing factors.
How do payload, trailer weight, and aerodynamics influence mpg?
Payload and trailer weight increase rolling resistance and required tractive effort, raising fuel use. Aerodynamic drag grows exponentially with speed; a poorly shaped trailer or high ride height slashes mpg on the interstate. Together, these are the biggest killers of real‑world fuel economy.
Why is a 75‑mph test a useful benchmark for U.S. interstate driving?
Many U.S. interstates have speed limits in the 65–75 mph range, and sustained speeds near 75 mph reveal aero and gearing impacts clearly. The test stresses cooling, transmission lock‑up, and sustained powertrain efficiency—conditions that matter most for long‑distance buyers and fleet operators.
Why doesn’t unloaded highway mpg predict towing mpg accurately?
Unloaded mpg reflects low rolling resistance and minimal aerodynamic penalty. Towing adds trailer drag, weight, and often higher rpm on grades—factors that dramatically change consumption. Towing mpg depends heavily on trailer shape, weight, and route profile, so unloaded figures are only a baseline.
Can you give a real‑world towing mpg example for a gas 2500 4×4?
In long‑distance testing, a gasoline 2500 4×4 towing a small motorcycle trailer has averaged around 11 mpg over mixed highway routes. That figure depends on load, speed, grade, and wind; heavier trailers or mountainous routes push mpg lower.
How do sustained climbs and high rpm impact fuel burn on mountain passes?
Climbs require sustained power and often higher rpm, which increases fuel flow significantly. Diesels typically handle climbs more efficiently due to greater torque at low rpm, but very steep grades still penalize all powertrains. Engine braking, transmission strategy, and proper gearing influence fuel use during descents and climbs.
Does paying extra for a diesel engine pay off over time?
It can, depending on miles, towing frequency, and fuel prices. For heavy highway users, a diesel’s better mpg and longevity often offset higher upfront cost and option premiums over 50,000–100,000 miles. Break‑even calculations should include purchase premium, fuel savings, maintenance, and resale values.
What upfront and option costs most change the diesel break‑even point?
Engine upgrade fees, tow packages, upgraded axles, and emissions equipment add to the upfront price. High‑output packages and heavy‑duty cooling also raise cost. Those line‑item options are the main determinants of how quickly fuel savings recover the premium for a diesel engine.
How should I choose between diesel and gas based on my job?
Choose diesel if you tow frequently, carry heavy payloads, or run many highway miles annually. Opt for gasoline if you do light towing, have lower annual mileage, or prioritize lower purchase price and simpler maintenance. Match engine choice to your typical duty cycle for the best ownership outcome.
