Diesel Over $5 in May, Nine Steps to Push Your Fleet Past 7 MPG

How much can a small fleet save by improving fuel economy right now?

Diesel averaged over $5 per gallon in May 2026, according to the U.S. Energy Information Administration. A five-truck fleet running 100,000 miles per year per truck at the national average of 6.91 MPG burns 72,359 gallons annually. At $5 per gallon, that's $361,795 in fuel. Push that same fleet to 10 MPG and the bill drops to $250,000, a $111,795 annual savings. The gap between average and achievable fuel economy is now worth more than two driver salaries.

Fleet managers cannot control the price per gallon. They can control miles per gallon. The national average MPG is 6.91, but fleets that prioritize fuel economy regularly achieve 10-plus MPG, according to industry data cited by Gino Fontana, a fleet technology consultant. The Department of Energy's SuperTruck 1 and 2 programs demonstrated trucks achieving 10.7 to 16 MPG under real-world conditions. The technology exists. The question is whether small fleets are using it.

What driver behaviors cost the most fuel?

Drivers still control a significant portion of fuel economy despite advances in truck technology. Speeding, hard braking, and hard starts consume fuel at rates that compound over a week. A driver who runs 5 mph over the fleet speed limit burns roughly 0.3 gallons more per 100 miles. Over 2,500 miles per week, that's 7.5 gallons, or $37.50 at $5 diesel. Multiply by 52 weeks and one driver costs the fleet $1,950 annually in avoidable fuel spend.

Fleets should re-engage drivers on fuel economy and consider incentivizing improvement. Fontana recommends tying bonuses or recognition to MPG gains. A $50 monthly bonus for drivers who beat their prior quarter's MPG by 5% costs $600 per driver per year. If that driver saves 400 gallons annually by moderating speed and braking, the fleet nets $1,400 at $5 diesel.

How much does idling cost per hour?

A typical Class 8 truck idles at approximately 0.8 gallons of diesel per hour. A driver who idles 10 hours per week burns 416 gallons per year idling, or $2,080 at $5 per gallon. Automatic engine shut-off mechanisms, idle timers, and auxiliary power units can cut that time without compromising driver comfort. Fontana suggests incentivizing drivers who reduce idle time, similar to MPG bonuses.

Idle reduction is one of the few fuel-saving measures a dispatcher can track in real time through telematics. Fleets that set idle alerts and review weekly reports see measurable drops in unnecessary engine run time. A 50% reduction in idle time for a five-truck fleet saves 1,040 gallons per year, or $5,200 at current diesel prices.

What electronic engine parameters improve fuel economy?

Electronic engine parameters can be set to control speed, reduce idling, and optimize shift points. Many fleets set parameters once and never revisit them. Fontana recommends checking that parameters have not been reset or tampered with, particularly after maintenance or software updates.

Speed limiters are the most direct parameter. Capping road speed at 65 mph instead of 70 mph saves roughly 0.5 MPG on highway runs. For a truck running 120,000 miles per year, that's 869 additional gallons consumed at 70 mph versus 65 mph, or $4,345 at $5 diesel. Progressive shift programming and cruise control lockouts also contribute to fuel savings, though the gains are smaller and harder to isolate.

Why fuel economy matters more now than in 2023

Fuel comprises a significant percentage of a fleet's operating budget. At $3 per gallon, fuel was the largest line item but still left margin for error. At $5 per gallon, fuel crowds out maintenance, insurance, and driver pay in the budget. A 10-truck fleet that averaged $600,000 in annual fuel costs in 2023 now faces a $1 million fuel bill at the same mileage and MPG. The $400,000 difference is larger than most small fleets' annual profit.

Diesel prices spiked in May 2026 as Brent crude jumped above $99 per barrel after U.S. strikes on Iran. Crude has since pulled back to the low $90s, but diesel lags crude price movements by 10 to 14 days. Small fleets should expect $5-plus diesel through mid-June at minimum. Fuel economy improvements that seemed marginal at $3 diesel now determine whether a truck turns a profit on a load.

What a 1 MPG improvement is worth to a 10-truck fleet

A 10-truck fleet running 100,000 miles per year per truck at 7 MPG burns 142,857 gallons annually. At $5 per gallon, that's $714,285 in fuel. Improve fleet-wide MPG to 8 and the same mileage requires 125,000 gallons, or $625,000. The 1 MPG gain saves $89,285 per year. That's enough to cover a full-time mechanic, a used truck payment, or a 15% raise for every driver.

The path to 8 MPG is not exotic. It's driver engagement, parameter audits, and idle reduction. Fontana's nine recommendations are operational, not capital-intensive. Fleets that treat fuel economy as a weekly priority rather than a quarterly review close the gap between 6.91 MPG and 10 MPG faster than fleets that wait for diesel to fall back below $4.