Truck Fuel Cost Per Mile: The Formula, a Table at $6.35 Diesel, and What Speed Does

At the EIA’s average on-highway diesel price of $6.352 a gallon (week of October 26, 2026), a truck that gets 6 mpg burns $1.06 of fuel every mile. Drop to 5 mpg and it is $1.27. Fuel cost per mile is price divided by miles per gallon, and speed is the part of that fraction you can change without touching the engine.

How do you calculate truck fuel cost per mile?

Divide the price of a gallon by the truck’s miles per gallon.

Fuel cost per mile = price per gallon / miles per gallon

For annual cost, multiply by miles driven. Or divide miles by mpg to get gallons used, then multiply by the price. Use your own mpg from fuel card and odometer data, not the engine display, and use what you actually pay per gallon. The price in this article is the national average from the EIA’s weekly diesel series, which was $6.352 for the week of October 26, 2026. It was $3.477 in the week of January 5, and the record is $6.529 in the week of September 21, 2026, the highest in a series that starts in 1994.

What is the fuel cost per mile at different mpg?

Here is the formula applied at $6.352 a gallon. The mpg values are examples to show the spread. Look up your own.

Truck mpg	Fuel cost per mile	Gallons per 100,000 miles	Fuel cost per 100,000 miles
5.0	$1.27	20,000	$127,040
6.0	$1.06	16,667	$105,867
6.5	$0.98	15,385	$97,723
7.0	$0.91	14,286	$90,743
8.0	$0.79	12,500	$79,400

Going from 5 mpg to 8 mpg cuts fuel cost per mile by about 38%, and on 100,000 miles the gap is $47,640 a truck. To see what happens at your own price, try the US fuel price and cost calculator, which uses the EIA weekly data.

How does speed change your mpg?

A lot, at highway speeds. The EPA’s SmartWay program says in its driver training fact sheet that a heavy truck driving 65 mph instead of 55 mph can use up to 20% more fuel. Their example truck gets 6 mpg.

Take that as an upper bound for a truck at 6 mpg. Using 20% more fuel for the same miles means about 5 mpg. At $6.352 that moves the cost from $1.06 to $1.27 a mile, or about $21,000 on 100,000 miles. Your result depends on the truck, load, terrain and how much of the route is at speed. The EPA says “up to”, and so do we.

Does a speed limiter save fuel across a whole fleet?

Less than the headline figure, because it only changes the fast miles. A one-year trial by CE Delft for Novem (2009), covering 177 vans and 30 trucks, found an average 5% fuel saving after speed limiters were fitted. That is a fleet average. Some drivers were already slow and some were not.

Worked through with the numbers above, for a truck covering 100,000 miles a year at 6 mpg:

• Fuel use: about 16,670 gallons.
• Fuel cost at $6.352: about $105,900.
• A 5% saving: about 830 gallons, or about $5,290 a truck a year.
• Across 20 trucks: about $105,900, close to one truck’s annual fuel bill.

That is an illustration at one price. At a lower diesel price the saving falls in proportion, and at a higher one it rises.

What else is in the fuel number?

Idling. The EPA fact sheet says a heavy-duty engine burns about 0.8 gallons an hour idling. At $6.352 that is about $5.08 for each hour, with zero miles. If your cost per mile looks high, check idle hours before you blame the road. Speed and idle are separate levers, and a limiter only acts on speed.

Your total cost per mile has more in it than fuel: drivers, insurance, maintenance, tires and equipment. Use your own books for the full number.

Where can a speed limiter fit?

If your mix includes older trucks, vans or pickups with no fleet speed setting, or you want one policy for everything, a sealed aftermarket limiter is the option. On a modern heavy truck you can often set a maximum road speed in the engine computer instead; our guide to engine setting or aftermarket governor sets out the choice. Product details are in truck and van speed limiters. Any truck with an electronic (drive-by-wire) throttle takes the DBW unit, whatever the maker. Nothing here is a promise of a saving for your trucks. For legal context, see the US truck speed limiter law guide.

Frequently Asked Questions

How do I calculate fuel cost per mile for a truck?

Divide the price per gallon by miles per gallon. At $6.352 a gallon and 6 mpg, that is $1.06 per mile.

What is a typical fuel cost per mile for a semi truck?

It depends on mpg and the diesel price. At $6.352 a gallon, 5 mpg costs $1.27 a mile, 6.5 mpg costs $0.98 and 8 mpg costs $0.79. These mpg values are examples, not an industry average.

How much more fuel does a truck use at 65 mph than at 55 mph?

EPA SmartWay says up to 20% more. The actual figure depends on the truck, load and route.

How much does idling cost per hour?

The EPA gives about 0.8 gallons an hour for a heavy-duty engine. At $6.352 a gallon, that is about $5.08 an hour.

Where do I find the current diesel price?

The EIA publishes a weekly US average on-highway diesel price. Our diesel and gas price tool shows the series back to 1994 and a cost calculator.

How do US fleets buy AutoKontrol speed limiters?

Through Scorpion, our parent group’s US team. Start with the quote form, and fitting is agreed per job, by your own technicians or our engineers and partners.

Put a number on your fuel bill

Every 10 cents per mile of fuel is $10,000 on a 100,000-mile truck, and speed is one of the few inputs you control. Tell us what you run and how many vehicles, and we will match a limiter to each one and price it. Get a quote or book a free consultation. How US fleets buy is set out on our US speed limiters page.

AutoKontrol has made speed limiters in Britain since 1985 and supplies fleets in more than 50 countries, with approvals including ISO 9001, UTAC, TÜV and VCA.