In the world of long-haul transportation, fuel efficiency isn’t just a buzzword, it’s a bottom-line issue. Whether you’re managing a fleet or driving solo, every extra mile per gallon can mean thousands of dollars in annual savings. With diesel prices staying high and environmental regulations tightening, choosing a fuel-efficient semi truck has never been more important.
Diesel costs fluctuate daily, but the average U.S. truck driver spends over $70,000 annually on fuel alone. A semi truck that delivers even 1 more mile per gallon can save over $10,000 each year in operating costs. That’s why models like the Freightliner Cascadia Evolution and Kenworth T680 Advantage have become favorites for those seeking both power and efficiency.
Fuel-efficient trucks not only reduce costs, they help the planet. Advanced aerodynamic designs and cleaner engines cut CO₂ emissions, supporting both EPA SmartWay certification and corporate sustainability goals. Many states even offer tax incentives or rebates for businesses operating greener fleets.
A modern semi truck’s fuel economy ranges from 6 to 10 miles per gallon, depending on load, driving style and terrain. While that may sound modest, remember, these trucks can carry up to 80,000 pounds of freight. Fuel efficiency is typically expressed as miles per gallon (MPG) or fuel cost per ton-mile, giving fleet managers a better picture of operational savings.
Several variables affect fuel economy:
After comparing data from manufacturers, fleet reports, and on-road tests, here are the most fuel-efficient semi trucks available in 2025.
MPG: Up to 10+ MPG
Equipped with the Detroit DD15 engine and aerodynamic front fascia, the Cascadia Evolution remains a top pick. It uses low rolling resistance tires, a side skirt design and active cruise control to minimize drag and boost real-world mileage.
MPG: 9 MPG (average)
With the PACCAR MX-13 engine and Eaton Fuller Advantage 10-speed automated transmission, the T680 Advantage optimizes fuel delivery while maintaining horsepower. Optional aero fairings and wheel covers enhance its aerodynamic profile.
MPG: 9.5–10 MPG
The Peterbilt 579 is all about balance, fuel efficiency, comfort and technology. The PACCAR Powertrain and 12-speed automated transmission help it deliver top performance, while the digital dash display aids efficient driving.
MPG: 8.8–9.2 MPG
Known for its driver comfort and I-Shift automated transmission, the Volvo VNL 860 pairs smooth performance with reduced fuel consumption. Its aerodynamic hood and deflectors cut drag while offering outstanding safety features.
MPG: 8.5 MPG
The Anthem’s MP8 engine and mDrive transmission are tuned for torque and fuel savings. Its bold, aerodynamic design reduces air resistance by 3% over earlier models and its advanced idle-reduction system saves fuel during stops.
MPG: 8 MPG
This reliable workhorse blends Cummins X15 Efficiency engines with aerodynamic mirrors, low-drag hood and optimized front bumper. Perfect for fleets balancing efficiency and durability.
MPGe: Equivalent of 20+ MPG
As electric trucks enter the market, the Tesla Semi leads the charge with near-zero emissions and massive torque. While charging infrastructure is growing, this EV truck offers the lowest operating cost per mile among all models.
MPGe: 18–20 MPGe equivalent
Built for regional hauls, the Freightliner eCascadia offers a sustainable solution with zero tailpipe emissions, ideal for companies transitioning to electric fleets.
| Model | Engine | Transmission | Fuel Type | MPG / MPGe | Best For |
| Freightliner Cascadia Evolution | Detroit DD15 | Automated | Diesel | 10+ | Long Haul |
| Kenworth T680 Advantage | PACCAR MX-13 | Eaton 10-Speed | Diesel | 9 | Fleet Efficiency |
| Peterbilt 579 | PACCAR Powertrain | 12-Speed Auto | Diesel | 9.5 | Comfort & Tech |
| Volvo VNL 860 | D13 w/ I-Shift | Automated | Diesel | 9 | Safety & Comfort |
| Mack Anthem | MP8 | mDrive | Diesel | 8.5 | Heavy Loads |
| International LT | Cummins X15 | Automated | Diesel | 8 | All-Purpose |
| Tesla Semi | Dual Motor | Electric | Electric | 20 MPGe | Sustainability |
| Freightliner eCascadia | Dual Motor | Electric | Electric | 18 MPGe | Regional Hauls |
Lightweight, durable and equipped with a variable speed water pump, the DD15 engine improves efficiency by 3%. It’s a top choice for fleets prioritizing uptime.
This engine shines for mid-range torque and fuel efficiency, making it ideal for both day cabs and sleepers.
Built for high mileage and low maintenance, this engine combines turbo compounding and predictive cruise control for optimal performance.
For short routes, box trucks like the peterbit, freightliner, Isuzu NPR, Ford E-Transit and Hino 195 deliver exceptional mileage. The E-Transit electric model offers near-zero emissions and lower lifetime costs for urban delivery operations.
At RK Truck Sales in Dallas, buyers can find both new and used fuel-efficient box trucks that match their operational needs.
Fuel efficiency isn’t just about saving diesel, it’s about smarter operations, greener fleets and better profits. Whether you’re upgrading your rig or expanding your fleet, RK Truck Sales in Dallas has the most fuel-efficient semi trucks ready for the road.
The Freightliner Cascadia Evolution and Peterbilt 579 consistently rank as the most fuel-efficient semi trucks in 2025. The Freightliner Cascadia Evolution delivers over 10 MPG in optimal highway conditions, thanks to its Detroit DD15 engine, aerodynamic body design and predictive cruise control.
Meanwhile, the Peterbilt 579 combines performance and comfort with its PACCAR Powertrain, achieving close to 10 MPG on long-haul routes. These models are especially popular among owner-operators and fleet managers looking to maximize profitability through better truck fuel efficiency.
Pro Tip: RK Truck Sales Dallas carries both new and pre-owned models of these fuel-efficient trucks for buyers across Dallas.
Most semi trucks average between 6 and 10 miles per gallon (MPG). However, newer models equipped with aerodynamic enhancements, automated transmissions, and eco-friendly engines can exceed 10 MPG on flat terrain with optimal loads.
Here’s a quick breakdown:
Factors that influence fuel economy include cargo weight, driving speed, tire pressure, wind resistance and engine tuning. Maintaining your truck properly and using efficient driving techniques can drastically improve fuel performance.
When it comes to fuel-efficient semi truck engines, three names dominate the market:
These engines are engineered to minimize fuel waste and extend maintenance intervals, helping fleets save both fuel and time on the road.
Improving truck fuel efficiency doesn’t always mean buying a new rig, simple changes can make a big difference.
Here are proven strategies to boost MPG:
Fleet managers at RK Truck Sales Dallas often recommend combining aerodynamic upgrades with driver training for maximum long-term savings.
Yes, electric semi trucks are significantly more efficient than their diesel counterparts. Models like the Tesla Semi and Freightliner eCascadia achieve the equivalent of 18–20 MPGe, compared to diesel trucks that average around 8–9 MPG.
Electric trucks convert up to 90% of battery energy into motion, while diesel engines use less than 45% of their fuel energy for propulsion. They also eliminate fuel costs, reduce maintenance (no oil changes or exhaust systems) and qualify for federal clean energy incentives.
While electric models currently have limited range and higher upfront costs, they’re ideal for regional or short-haul operations and represent the future of fuel-efficient commercial trucking.
Fuel accounts for up to 40% of a fleet’s operating expenses, so improving fuel economy can directly impact profits. For example, if a truck drives 100,000 miles a year, improving fuel efficiency from 6 MPG to 8 MPG could save roughly 4,000 gallons of diesel annually — that’s about $16,000 in savings per truck per year (at $4/gallon diesel).
Investing in fuel-efficient trucks or retrofitting your current fleet with aerodynamic and telematic solutions delivers immediate ROI and long-term sustainability benefits.
Trucks known for both efficiency and resale value include:
These models retain up to 60% of their value after five years, especially when maintained with full service records. Fuel-efficient engines like PACCAR MX-13 and Detroit DD15 also enhance resale desirability due to their reliability and lower lifetime fuel costs.
While semi trucks are designed for long-distance hauling, box trucks (like the Isuzu NPR or Ford E-Transit) are optimized for urban deliveries. Box trucks generally achieve 10–14 MPG for diesel and 50–120 MPGe for electric versions. They’re perfect for businesses that operate within cities and want to reduce fuel and maintenance expenses without compromising payload capacity.
Absolutely, with proper maintenance and tuning, used semi trucks can remain highly fuel-efficient. Fleet operators who invest in aerodynamic retrofits, fuel-efficient tires and updated engine control modules (ECMs) often see MPG improvements of 5–10%.
At RK Truck Sales Dallas, each pre-owned truck undergoes a multi-point inspection to ensure top fuel performance before resale.
You can find top-rated fuel-efficient semi trucks at RK Truck Sales Dallas, your local authority for commercial truck sales, trade-ins, and financing. We specialize in Freightliner, Peterbilt, Kenworth, Volvo and International box trucks, both new and used, all inspected for fuel performance and reliability.
Visit our dealership in Dallas, TX or browse inventory online at RK Truck Sales to find the perfect fuel-efficient truck for your business.
John Hendricks is a commercial truck enthusiast and content writer for RK Truck Sales. With a deep understanding of the trucking industry and market trends, John Hendricks specializes in educating visitors on used and new box trucks. When he’s not writing, you’ll find him visiting truck lots or chatting with industry pros across Dallas.
