The cost per mile most fleet owners cannot actually produce
Ask the owner of a small haulage or field-service business a simple question, and watch the pause: what does it cost you, per mile, to put fuel in your vehicles? Most cannot answer it with a real figure. They can tell you what they spent last month in total, and they can find the fuel-card statement, but the per-mile, per-vehicle number that a finance professional would actually want is usually a guess.
That gap matters more than it looks, and US operators, who benchmark fleet costs unusually closely, have started treating it as a discipline rather than an afterthought.
The number, and why it is not small
The American Transportation Research Institute puts the average operational cost of running a heavy truck in the United States at roughly $2.34 per mile in its most recent annual analysis, with fuel accounting for about $0.48 of that, a little over a fifth of the total and typically the second-largest line after driver pay. National on-highway diesel has held around $4.60 to $4.80 a gallon through 2026.
Put those together and the point is obvious. Fuel is one of the largest single costs a fleet carries, it moves with the market, and it is almost entirely dependent on how the business buys and manages it. A cost that big, that volatile, and that controllable deserves a real model, not a shrug.
Why guessing is expensive
When fuel is treated as a lump sum rather than a modelled cost, three things tend to go wrong, and all three land on the finance function.
Quotes get padded or underpriced. Without a reliable fuel cost per mile or per job, operators either add a safety margin that loses them work or leave it out and absorb the overrun. Neither is a decision; both are accidents.
Waste hides. The labour cost of vehicles leaving site to refuel, the shrinkage from a tank nobody meters, the premium paid at retail forecourts over bulk or delivered fuel, none of it surfaces if the only number anyone tracks is a monthly total.
Comparisons become impossible. If you cannot state your current cost per mile, you cannot evaluate whether a different refuelling arrangement, route, or supplier would actually save money. You are negotiating blind.
The case for modelling it first
The useful habit US operators have adopted is to model the number before making any change, so that a decision can be measured against a baseline rather than a feeling.
That does not require enterprise software. At its simplest it means taking your fleet size, average mileage, and current price per gallon or litre, and working out what fuel really costs you today, then testing what a different buying model would do to that figure. Free tools exist for exactly this: a fleet fuel cost checker lets an operator plug in their own numbers and see the delivered-versus-pump comparison in a few minutes, which is often the first time the true cost has been laid out in one place.
The value for a finance readership is not the specific tool. It is the reframing. Fuel stops being a cost you discover at month end and becomes a variable you can forecast, defend in a bid, and challenge a supplier on.
The transferable lesson
None of this is US-specific. The diesel price and the tax treatment differ across the Atlantic, but the mechanism is identical everywhere: an operator who can state their cost per mile can manage it, and one who cannot is simply hoping the market stays kind.
For anyone advising SMEs in haulage, construction, agriculture, or distribution, this is a low-effort, high-return question to put to a client. Can they produce their fuel cost per mile? If not, that single gap is quietly shaping their pricing, their margin, and their ability to compete on the next tender. Closing it starts not with a new supplier or a new truck, but with modelling the number they already have.
The firms that treat fuel as a figure to be calculated, rather than a bill to be paid, tend to find the savings were sitting in the arithmetic all along.