Fuel surcharge exists so that a rate agreed in March is not destroyed by a fuel price in June. That is the theory. In practice a surcharge is a formula somebody else wrote, and whether it protects you depends entirely on inputs you did not choose.
The three inputs that decide everything
- The index it references — usually a published regional or national average diesel price, updated weekly.
- The baseline, or peg: the fuel price at which surcharge is zero. Everything above the peg generates surcharge; everything below generates nothing.
- The assumed fuel economy. The formula divides the price difference by an MPG figure to get a per-mile surcharge — and that figure is an assumption about your truck.
Change any one of those and the same diesel price produces a materially different surcharge. A generous-sounding percentage attached to a high peg can pay less than a modest one attached to a low peg.
Loaded miles or all miles
Surcharge is normally paid on loaded miles. You burn fuel on empty ones too. That gap is the same one that distorts cost per mile, and it means a surcharge can look like full protection while covering only the paid portion of your running.
It is not a reason to refuse the load. It is a reason to treat surcharge as partial coverage rather than a hedge, and to price the linehaul accordingly.
What to check before accepting
- Is the surcharge stated as a figure, or as a formula you would have to reconstruct? A figure you cannot verify is a figure you cannot dispute.
- Which index and which week — a surcharge referencing a stale week during a rising market silently underpays.
- Is it included in the linehaul rate or paid on top? The same total looks very different depending on the answer, and only one of them adjusts if fuel moves.
- Does it appear on the rate confirmation at all? If it was agreed on the phone and is not in the document, it does not exist.
Then do the only test that matters: total revenue for the load, divided by every mile the truck will turn, against your own cost per mile. Surcharge is a component of that number, not a separate win.