A fuel surcharge is a separate line-item fee a freight carrier adds to a shipping invoice to cover diesel price swings, and understanding how fuel surcharges work in trucking comes down to four things: the diesel index the carrier uses, the base price built into the contract, the fuel-economy peg for the equipment, and whether the charge is billed per mile or as a percentage of the linehaul rate. Fuel typically accounts for 25 to 30 percent of a carrier’s operating cost, so most contracts split that expense out of the base rate and let it float with a published index, resetting weekly.
The Basic Calculation
Every surcharge starts with two reference points. The first is a base fuel price, the diesel cost below which no surcharge applies. Industry baselines usually sit between $1.20 and $1.50 per gallon, though older contracts sometimes set the floor as high as $2.50. The second is a miles-per-gallon peg, a standardized fuel-economy figure for the equipment type rather than the actual mileage any particular truck gets. A standard dry van is normally pegged at 6.0 MPG.
The math is straightforward. Subtract the base price from the current diesel price, then divide by the MPG peg. If diesel sits at $3.85 and the contractual base is $1.25, the difference is $2.60. Divided by 6.0 MPG, that produces a surcharge of roughly $0.43 per mile. On a 1,200-mile haul, the surcharge adds about $520 to the freight bill.
The current diesel price comes from the U.S. Energy Information Administration, which surveys roughly 400 retail outlets every Monday and publishes the national average around 5:00 p.m. Eastern the same day.1U.S. Energy Information Administration. Gasoline and Diesel Fuel Update That weekly reading is what most contracts plug into the formula.
Per-Mile Versus Percentage-Based Billing
Truckload carriers almost always express the surcharge as cents per mile using the formula above. Less-than-truckload and parcel carriers work differently. They publish surcharge tables that assign a percentage of the linehaul rate to each diesel price band. When diesel falls in the $3.80 to $3.99 range, an LTL carrier might apply a 27 percent surcharge to the net linehaul charge; if the price climbs into the $4.00 to $4.19 band, the percentage jumps to 28.5 percent. These tables update weekly against the same EIA index.
The percentage method is simpler for LTL because those shipments involve partial loads, multiple stops, and variable mileage that make a per-mile calculation awkward. For shippers comparing quotes across carriers, the honest comparison is total cost per shipment. A carrier offering a lower linehaul rate with a steep surcharge percentage can end up more expensive than one quoting a slightly higher base with a modest per-mile surcharge.
Equipment Type and Regional Diesel Prices
Not all trucks burn fuel at the same rate, and the MPG peg reflects that. Refrigerated trailers run a diesel-powered cooling unit on top of the tractor engine, so the industry peg drops to about 5.5 MPG. Flatbeds, heavier and less aerodynamic, peg at around 5.0 MPG. The lower the peg, the higher the surcharge per mile: a reefer surcharge on a given lane will always run higher than a dry van surcharge on the same lane.
Region matters too. The EIA breaks diesel data into five Petroleum Administration for Defense Districts: East Coast, Midwest, Gulf Coast, Rocky Mountain, and West Coast.1U.S. Energy Information Administration. Gasoline and Diesel Fuel Update West Coast diesel routinely runs $0.30 to $0.50 higher than the Gulf Coast average. More sophisticated contracts peg the surcharge to the regional PADD price instead of the national average, so the charge tracks closer to what the carrier is actually paying at the pump. If your freight moves primarily in PADD 5 territory and the contract still uses the national index, you’re probably undercharging on westbound loads and overcharging on eastbound returns.
What the Freight Contract Should Say
A well-drafted surcharge clause covers four things: the index source, the base price, the MPG peg, and the trigger point. The trigger is the diesel price at which the surcharge activates. If the base is $1.25 and the trigger is $1.50, diesel has to exceed $1.50 before any surcharge shows up on the invoice. Some agreements set the base and trigger at the same price; others build in a buffer.
The surcharge should appear as a separate line item on the freight invoice or bill of lading, distinct from the linehaul rate. That separation lets the shipper audit each component against the published index. No federal agency regulates the size or structure of fuel surcharges in general freight; it is a matter of contract. The FMCSA has stated publicly that it does not have authority to mandate how surcharges are set or passed through in commercial trucking. Disputes over surcharge calculations go through the contract’s own arbitration or litigation provisions, not a federal complaint process.
Contracts should also specify which week’s EIA data applies to each invoice. A one-week lag is common: Monday’s published price sets the surcharge for shipments tendered the following week. Without this detail pinned down, arguments about which price applies to a given load become inevitable on weeks when diesel moves sharply.
Owner-Operator Pass-Through Rules
Owner-operators leasing their equipment to a motor carrier get specific federal protections around fuel costs. Under 49 CFR 376.12, any written lease between an independent owner-operator and a carrier must spell out which party pays for fuel, fuel taxes, tolls, permits, and similar expenses.2eCFR. 49 CFR 376.12 – Lease Requirements Compensation must appear clearly on the face of the lease or an attached addendum, and the addendum has to be delivered before the trip begins.
Charge-back items get their own requirement. The lease must list every expense the carrier initially pays but later deducts from the owner-operator’s settlement, along with how each deduction is calculated, and the carrier must provide the documents needed to verify those charges.2eCFR. 49 CFR 376.12 – Lease Requirements In practice, that means if a carrier collects a fuel surcharge from a shipper on a load hauled by a leased owner-operator, the settlement statement should show what was collected and what portion, if any, was passed through. The regulation doesn’t explicitly require a dollar-for-dollar pass-through, but it does require enough transparency for the owner-operator to see where the money went.
How Surcharge Revenue Is Taxed
Fuel surcharge revenue collected from shippers is ordinary business income to the carrier. It gets reported like any other freight revenue and is subject to normal income tax. The surcharge label doesn’t create any special tax treatment; the IRS does not distinguish the linehaul rate from the surcharge component when calculating taxable income.
Separately, carriers who use fuel in certain qualifying activities may be able to claim a federal excise tax credit on Form 4136. The credit belongs to the “ultimate purchaser” of the fuel, meaning the entity that bought and consumed it, regardless of whether a customer reimbursed the cost through a surcharge.3Internal Revenue Service. Instructions for Form 4136 (2025) If you deduct the full cost of fuel including excise taxes as a business expense and then receive an excise tax credit or refund, that credit has to be included in gross income to prevent a double benefit.