Diesel6 min read
The fuel line on a freight bill is a formula, not a mood
Diesel moved. The surcharge moved. Here is the arithmetic most contracts are actually doing, and the places it gets abused.
Most highway contracts peg the surcharge to the EIA weekly on-highway diesel average — the same series that printed $6.529 for the week of September 21, 2026. A simple version of the formula is: take today's DOE price, subtract a base price written in the contract, and divide by the truck's miles per gallon. That result is dollars per mile.
Say the base in the contract is $1.20 and the truck averages 6.5 miles per gallon. ($6.529 − $1.20) ÷ 6.5 is about $0.82 per mile. On a 500-mile run that is roughly $410 of fuel surcharge, on top of the linehaul rate. Change the miles per gallon or the base and the invoice changes. There is a calculator on the diesel desk set to the latest weekly index so you can see the levers.
What people argue about
- The base price. A low base makes the surcharge look huge even if the underlying haul rate was discounted to match. Read both numbers.
- The miles per gallon. A contract that assumes 5 mpg collects more per mile than one that assumes 7. It may or may not match the truck.
- Which week's index applies. Serious contracts name the EIA week, so nobody substitutes a convenient truck-stop receipt.
- Empty miles and multi-stop routes. If the formula only pays the loaded miles, the carrier eats the fuel to reposition the truck.
A surcharge is not a tax, and it is not optional just because fuel “feels high.” If it is in the contract, it is part of the price. If it is not in the contract, a surprise fuel line is a dispute, not a law of nature.
Sources
The Ro-Mac Brief summarizes public reporting for a general reader. Figures can be revised by the agency that published them. This is not legal advice.
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