3 min read · updated October 11, 2026
Does your fuel surcharge really cover your fuel?
How a fuel surcharge is calculated, why it often pays less than your fuel costs, and a two-minute check with 2026 diesel prices.
A fuel surcharge (FSC) is money added to a load to cover the part of fuel that is above a "normal" price. Many owner-operators assume it covers their fuel. It usually covers part of it. In 2026, with diesel near record prices, the gap got expensive.
How the surcharge is calculated
Most contracts use the same formula:
Surcharge per loaded mile = (diesel price this week − base price) ÷ contract miles per gallon
The base price is often $1.25 to $1.50 a gallon. The contract miles per gallon is often 6 to 7.5. Both numbers were set years ago, and neither is your truck.
Example. Diesel this week: $6.38 (EIA average, late September 2026). Base price in the contract: $1.25. Contract miles per gallon: 6.
Surcharge = ($6.38 − $1.25) ÷ 6 = $0.86 per loaded mile.
What your fuel really costs per loaded mile
Your fuel cost per mile is the price divided by your real miles per gallon. Then it has to be spread over loaded miles only, because empty miles burn fuel and get no surcharge.
Fuel per mile: $6.38 ÷ 6.5 = $0.98. Empty miles: 15%.
Fuel per loaded mile = $0.98 ÷ 0.85 = $1.15.
Surcharge $0.86 against fuel $1.15: the surcharge covers about 74%. The gap is $0.30 per loaded mile. At about 1,770 loaded miles a week, that is about $531 a week that has to come from the line-haul rate.
Why the gap happens
The base price. Everything below the base price is "yours". At $1.25, the first $1.25 of every gallon is never covered.
The contract miles per gallon. If the contract says 6 and you get 6.5, the surcharge is a little generous. If the contract says 7 and you get 6, you lose on every mile.
Empty miles. The surcharge is paid per loaded mile. Your fuel is burned on all miles.
Reefer fuel. A reefer unit burns diesel by the hour, not by the mile. No surcharge covers it.
The two-minute check
- Find the diesel price this week (the EIA publishes it every Monday).
- Find the base price and the miles per gallon in your contract or rate confirmation.
- Surcharge per loaded mile = (price − base) ÷ contract mpg.
- Your fuel per loaded mile = (price ÷ your mpg) ÷ (1 − your empty share).
- If line 3 is below line 4, the difference belongs in your rate.
Do this once when diesel moves a lot. The MY COST tab of the Miles to Money spreadsheet does this check every time you type a new diesel price, and shows the rate you need if fuel goes up another 50 cents, or down.
Sources
- EIA weekly diesel prices, via USAFacts and IndexBox
- FreightWaves, What is a fuel surcharge in trucking?
Example numbers. This guide is not tax, legal, accounting or financial advice.