Look at almost any LTL invoice and you'll find a fuel surcharge (FSC) — frequently 20–30% on top of the base rate. It's one of the largest line items on the bill, yet many shippers never verify it. Here's how it works.
What the fuel surcharge is
The FSC is a variable charge carriers add to offset changing diesel prices, so their base rates can stay relatively stable. Instead of renegotiating rates every time fuel moves, the carrier applies a percentage that floats with the market.
Where the number comes from: the DOE index
Most LTL fuel surcharges are tied to the U.S. Department of Energy (DOE) national average diesel price, published weekly by the Energy Information Administration (EIA). Each carrier publishes an FSC schedule in its rules tariff: a table that maps a range of DOE diesel prices to a surcharge percentage.
For example, a schedule might say: when diesel is $4.00–$4.09/gal, the surcharge is 28.5%; when it's $4.10–$4.19, it's 29.0%, and so on. The carrier looks up the current week's DOE price, finds the matching row, and applies that percentage.
What the surcharge applies to
This is a subtle but important point: the FSC is usually calculated on the base linehaul charge after discount — not on accessorials, and not on the undiscounted rate. Two carriers can quote the same headline discount but end up at different totals because of how and where their fuel surcharge applies.
How to sanity-check your invoice
- Find the DOE diesel price for the shipment's week (the EIA publishes it every Monday).
- Look up your carrier's FSC schedule in their rules tariff and find the matching percentage.
- Confirm the base it's applied to. Multiply the correct base by the correct percentage and compare to the billed amount.
A fuel surcharge that doesn't reconcile is worth a call to the carrier — either the wrong week's index was used, or it was applied to the wrong base.
Why it matters
Because the FSC is a percentage on a large base, small errors compound. Auditing fuel is one of the highest-return checks in LTL — and it's exactly the kind of line-item review that pays for itself quickly.
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