Diesel Price Forecast & Fuel Surcharge Math for 2026
Diesel softened through most of 2025, and the EIA forecast for 2026 keeps national averages in the $3.40–$3.80/gallon range. Here's how to use that to set a fuel surcharge that actually protects your margin.
The basic surcharge formula
Pick a baseline diesel price (most use the EIA national average). For every 6 cents diesel exceeds the baseline, add 1 cent per mile to your linehaul rate. For every 6 cents below, subtract 1 cent per mile. This roughly compensates for a 6 MPG truck.
Why most small carriers under-collect
- They forget to update the baseline weekly
- They use rate-confirmation surcharge that lags the spot market
- They don't itemize FSC on the invoice (so brokers contest it)
- They underestimate empty miles in the calculation
What automation gets you
A modern TMS pulls the EIA average automatically and applies your surcharge curve to every new load. The surcharge prints as a separate line item on the invoice — far harder for brokers to short-pay.
Sources & further reading
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