Speed vs fuel savings calculator

Speed is the fuel lever you control every day

Fuel economy depends on a lot of things you can't change on a given day: the truck, the trailer, the load, the wind and the road. Speed is different. It's the one you choose every minute you drive, and it has a big effect, because aerodynamic drag grows quickly as speed rises. A few miles an hour less can mean a noticeable difference in mpg.

Slower also means more hours on the road for the same miles, and for an owner-operator, time is money too. This speed vs fuel savings calculator puts both sides in front of you: the fuel each speed costs over your miles, the fuel saved by slowing down, the hours it adds, and what each of those extra hours is worth in saved fuel.

How the comparison is calculated

For each speed, fuel used is your miles divided by the mpg at that speed, and the cost is that times the diesel price. Driving time is miles divided by speed. The fastest speed is the baseline: the calculator shows how much each slower speed saves in fuel and how many hours it adds. Divide the fuel saved by the hours added and you get what slowing down pays per extra hour.

The mpg at each speed is the input that matters most. The starting values use a rule of thumb from a report sponsored by engine maker Cummins and widely repeated in trucking trade press such as FleetOwner: above 55 mph, each extra mile per hour costs about 0.1 mpg. FleetOwner notes the effect depends on aerodynamics and conditions, and can be about double for a truck with poor aerodynamics. Your own engine data is better than any rule of thumb, so replace the values with yours if you can. We checked the source in October 2026.

• EXAMPLE

  EXAMPLE YEAR

  100,000 miles at 62, 65 and 70 mph

  With an EXAMPLE diesel price of $4.00 and the rule-of-thumb mpg of 7.0, 6.7 and 6.2, fuel costs about $57,143 at 62 mph, $59,701 at 65 and $64,516 at 70. Running 62 instead of 70 saves about $7,373 and adds about 184 hours of driving, so slowing down pays about $40 for each extra hour.

Reading your result

The key number is the fuel saved per extra hour. Compare it with what an hour of your driving time earns. If slowing down pays more per hour than the extra time would earn hauling, the slower speed is worth it. If your hours are tight, because of the 11-hour driving limit or appointment times, the extra hours may cost you a load, and the math changes.

• +Big savings, few hours. Slowing down is an easy win. Most of the time the extra hours fit within your normal day.
• +Savings per hour lower than your hourly earnings. Speed may be worth more to you than the fuel, especially on tight schedules.
• +Very different mpg at each speed. Check your data. A big drop between two close speeds can point to gearing, aerodynamics or a mechanical issue.

Other ways speed affects your costs

Fuel isn't the only cost that rises with speed. Tires wear faster at higher speeds, brakes work harder, and stopping distances get longer. The truck stopping distance calculator shows how fast stopping distance grows. Many carriers and insurers also look at speed as a safety signal.

On the other side, slower speeds use more of your driving hours and the 14-hour window. On a tight appointment, a slower speed can push a delivery past its time, which can cost detention rights or even the load. Plan appointments around the speed you want to drive. For the fuel cost of a single trip, the trip fuel cost calculator works it out from miles, mpg and price.

Fuel, speed and the loads we book

Our dispatchers plan loads around legal hours and the speed you choose to run, so appointments don't depend on running fast. We count fuel on every mile, empty ones included, before we counter. You approve the loads, and the broker sends each rate confirmation directly to you. See how we work with owner-operators.

Fuel surcharges on some freight pay back part of the fuel cost when prices rise. The fuel surcharge calculator shows how much. Our guides to rates per mile and truckload spot rates cover the revenue side.