Diesel at $6.29: Protect Your Trucking Margin

The Number That Should Be in Your Pricing Meeting Today

EIA's latest published national average is $6.285 per gallon. That is an increase of $0.318 per gallon from the September 7 figure and $0.686 from August 31. The percentage is not the important part for an operator. The important part is what that change does to fuel cost per mile on the trucks you actually run.

At 6.0 mpg, $6.285 diesel is about $1.05 per mile in fuel alone. A $0.318-per-gallon weekly move adds about 5.3 cents per mile at that fuel economy. Across 1,000 miles, that is roughly $53 more fuel cost before you account for deadhead, tolls, maintenance, insurance, or driver pay. At fleet scale, small per-mile changes become real money very quickly.

Stop Pricing Freight From Last Month's Fuel Cost

Your cost per mile is not a permanent number. Fuel is one of the variables that can move fast, so a rate that worked three weeks ago can become a weak rate without the linehaul changing at all. Run a current fuel-cost-per-mile calculation before you accept the load, not after the truck is already committed.

• Current diesel price ÷ real-world loaded MPG = loaded fuel cost per mile.
• Add deadhead miles to the trip instead of pretending every mile is paid loaded mileage.
• Recalculate the trip using the actual fuel economy of the assigned truck when you have that data.
• Compare the resulting fuel cost with your full operating cost per mile before accepting the load.
• Record the result so your next quote starts from current numbers instead of memory.

Fuel Surcharges Are a Tool, Not a Magic Shield

There is no federal law requiring a carrier to use a fuel surcharge. OOIDA describes a fuel surcharge as a separate amount above the base freight rate that helps offset fuel increases above a defined baseline. That means the protection comes from the agreement and the formula, not from simply writing 'FSC' on an invoice.

DAT's current RateView methodology uses a baseline diesel price, compares it with the weekly DOE/EIA national average, and converts the difference into a per-mile amount using MPG. The exact baseline and formula can vary by contract, customer, equipment, and market, so do not copy someone else's surcharge table without checking whether its assumptions match your operation.

The Simple Fuel Surcharge Math Every Dispatcher Should Know

A clean starting formula is: (current diesel price − agreed baseline diesel price) ÷ MPG = fuel surcharge per mile. For example, if your contract baseline is $4.00, current diesel is $6.285, and your truck averages 6.0 mpg, the fuel gap is $2.285 per gallon. Divided by 6.0 mpg, that is about $0.38 per mile of fuel-cost difference. That is an example, not a universal industry rate. Your contract should define the baseline, mileage basis, update frequency, and treatment of empty miles.

Spot Market Loads Need a Different Conversation

Spot freight is usually quoted as an all-in number, which means the fuel component is buried inside the rate. DAT notes that this is a major reason spot and contract rates have to be compared carefully. If diesel moves sharply, do not assume a load board rate has automatically adjusted enough to preserve your margin.

For a spot load, work backward. Calculate your total trip miles, current fuel cost, deadhead exposure, tolls, accessorial risk, and operating cost per mile. Then decide the minimum all-in rate that makes the load worth taking. If the broker's number misses that floor, negotiate the total rate. Do not wait for a separate fuel-surcharge line that may never appear.

Deadhead Is Where Fuel Math Gets Ugly

A truck does not get better fuel economy because the miles are unpaid. If a 500-mile load requires 100 miles of deadhead to reach pickup, the truck has to recover fuel and operating costs over 600 actual miles. Treating the load as 500 miles makes the rate look better than it really is.

• Calculate loaded miles and deadhead miles separately.
• Use total trip miles for fuel and operating-cost calculations.
• Track deadhead percentage by lane, customer, and dispatcher.
• Use lane history to identify customers that consistently create expensive positioning miles.

Your Dispatcher Should See Fuel Cost Before Booking

Fuel should be part of the load-selection screen, not a month-end accounting surprise. A dispatcher should be able to see the offered rate, total trip miles, estimated fuel spend, deadhead, accessorial assumptions, and expected contribution before the truck is committed. That turns dispatch from load entry into margin control.

Watch the Fuel Market Without Chasing Every Headline

EIA's September 2026 Short-Term Energy Outlook shows an elevated diesel crack spread and says refinery outages, including lost refinery activity in Russia, are adding pressure to global petroleum markets. That is useful context, but an operator does not need to predict crude oil perfectly. You need a repeatable pricing process that reacts to the number actually hitting your cost model.

Build a Weekly Fuel Margin Routine

• Monday: pull the latest EIA national diesel average and update your pricing model.
• Monday: calculate fuel cost per mile for each major equipment class.
• Before booking: calculate total trip miles, including deadhead.
• Before accepting contract freight: verify the fuel-surcharge baseline and update frequency.
• Friday: compare estimated fuel cost with actual fuel spend by truck and lane.
• Monthly: review MPG, deadhead, fuel-card discounts, and the lanes where fuel is destroying margin.

Fuel Discounts Matter, But They Do Not Fix a Bad Rate

A fuel card discount can reduce the amount you pay at the pump, but it cannot turn an underpriced load into a profitable one by itself. Treat pump savings as a cost-control lever after you have confirmed the freight rate covers the operation. A 10-cent-per-gallon savings is useful; a load priced 30 cents per mile below your required contribution is a much bigger problem.

Use Your TMS to Close the Loop

The useful workflow is simple: quote the load, calculate expected fuel, dispatch the truck, capture actual fuel and miles, then compare expected versus actual margin. That history gives you a real operating baseline for future quotes. It also lets a fleet manager spot trucks with declining MPG, lanes with excessive deadhead, and customers whose rates no longer work when fuel moves.

What to Change This Week

Do not wait for the next quarterly review. Update the diesel number in your cost model. Recalculate fuel cost per mile. Check the fuel-surcharge language on your contract freight. Reprice lanes with heavy deadhead. Give dispatch a minimum all-in rate based on current operating costs. Then compare actual fuel spend against the estimate at the end of the week.

The load is not profitable because the rate looks good. It is profitable when the rate still works after the truck actually runs the miles.

FAQ

What Is the Latest U.S. Diesel Price?

As of September 21, 2026, the latest published EIA weekly U.S. on-highway diesel average is $6.285 per gallon for the week ending September 14. EIA publishes the national weekly series and regional figures as part of its gasoline and diesel price update.

How Do You Calculate a Trucking Fuel Surcharge?

A common per-mile method subtracts an agreed baseline diesel price from the current diesel price and divides the difference by the truck's MPG. Contracts can use different baselines, mileage assumptions, and update schedules, so the agreement controls.

Do Owner-Operators Have to Charge a Fuel Surcharge?

No federal law requires a carrier to use a fuel surcharge. If you operate on contract freight, the surcharge terms are negotiated with the customer or counterparty. On spot freight, fuel is commonly recovered through the all-in rate.

What MPG Should I Use for Trucking Fuel Cost?

Use your truck's actual recent fuel economy whenever possible. Industry examples often use around 6 mpg for a loaded big rig, but your equipment, weight, terrain, weather, speed, idle time, and empty miles can produce a different number.

How Can a Dispatcher Protect Profit When Diesel Jumps?

Use current fuel cost per mile, include deadhead, calculate the minimum acceptable all-in rate before booking, verify fuel-surcharge terms on contract freight, and compare estimated versus actual trip margin after delivery.