Trucking Fuel Discounts: Three Ways Enterprise Fleets Overpay at the Pump (With Real Numbers)

Fuel is the second largest operating expense in trucking, trailing only driver wages, and as of this week that expense looks nothing like it did six months ago. The U.S. Energy Information Administration's weekly diesel survey put the national average at $6.29 per gallon for the week ending September 14, 2026. In January, before this year's disruption began, the average was $3.52. That is a roughly 79 percent increase in eight months, and it is not a slow drift. Diesel jumped from the low $3 range to above $5 in the space of two weeks in early March, the sharpest short-term move the industry has seen since Russia's invasion of Ukraine in 2022.

The cause is the war between the United States, Israel, and Iran that began in late February 2026. Iran's disruption of the Strait of Hormuz and the Bab al-Mandab corridor, followed by the shutdown of the East-West Crude Oil Pipeline on September 11, has been described by the International Energy Agency as the largest supply disruption in the history of the global oil market, cutting into an estimated 39 percent of global trade and 31 percent of global shipments. The EIA now projects national distillate inventories will fall below 100 million barrels this month and stay there through much of 2027. This is not a spike that resolves itself by winter.

For a fleet director, this changes two things at once. First, every dollar figure attached to the fuel overpayment problems this site covered in March is now understated by roughly 70 percent, because the same percentage-based losses apply against a much larger fuel budget. Second, and this is the part almost nobody writing about fuel cards or fuel discounts is addressing directly, the speed of this shock exposed a structural weakness in how fuel surcharges are calculated that most carriers have never had reason to examine closely until now.

This article covers both. The three original overpayment problems, rescaled to current pricing, and the surcharge lag, which is new.

The Fuel Surcharge Lag: What Almost No One Is Telling Carriers

Fuel surcharges exist specifically to protect carriers from exactly this kind of event, a rapid, unpredictable move in diesel price that a linehaul rate negotiated months earlier could not have anticipated. The mechanism failed to keep pace this time, and the reason is structural rather than a matter of bad faith on any single broker or shipper's part.

Most surcharge agreements reset on a fixed cycle, weekly, biweekly, or monthly, and calculate the adjustment off a lagging benchmark, typically the prior week's EIA average. When diesel is moving 10 to 30 cents in a single week, which it did repeatedly in March and again through late August and September, a surcharge calculated off last week's number is already behind by the time it is applied. Ken Adamo, chief of analytics at DAT Freight and Analytics, documented this lag directly in the early weeks of the war: in the first ten days of the conflict, all-in freight rates had risen only 3 percent while diesel costs had already jumped considerably more, meaning carriers were absorbing the difference. Rates did eventually catch up, reaching a 10 percent all-in increase within a few more weeks, but that catch-up period is exactly where the exposure sits.

The dollar impact of that lag has been documented at the carrier level. One industry analysis found that owner-operators and small fleets were absorbing roughly $2,600 or more per truck per month in unrecovered fuel cost when diesel was at $5.37 a gallon, back in early April. That figure was measured against a price point nearly a dollar below where diesel sits today. The same research put a number on the mechanism itself: a fuel surcharge might cover 60 to 70 percent of a rapid increase, leaving the remainder to come directly out of operating margin. For a fleet running 30 trucks, even the lower end of that documented per-truck gap, extrapolated across a full month, is a meaningful five-figure hole that shows up nowhere on an invoice and never gets flagged unless someone goes looking for it.

The exposure is not evenly distributed. Jason Miller, professor of supply chain management at Michigan State University, has pointed out that carriers protected by well-structured fuel surcharge agreements are in a fundamentally different position than carriers running primarily on the spot market, where fuel cost recovery depends on rates adjusting in real time rather than through a contractual formula. Spot-heavy carriers absorb the full velocity of a shock immediately. Contract carriers absorb a partial, lagged version of it, with the size of the lag determined entirely by how their specific surcharge clause is written.

How to Check Whether Your Own Surcharge Is Actually Covering You

Most fleet directors have never audited their surcharge formula against a live event, because until this year there was rarely a reason to. The check is straightforward and worth running now regardless of what the formula says on paper.

Pull your surcharge agreements and identify three things for each one: the benchmark source, almost always the EIA weekly average, but confirm it, the reset cycle, weekly is common, some run biweekly or monthly, and the base price the formula was calibrated against when it was negotiated. Then compare your actual collected surcharge revenue over the past two months against what a real-time, same-day surcharge would have paid you using the actual EIA reading each week. The gap between those two numbers is your unrecovered fuel cost, and it is a number worth knowing precisely rather than estimating.

If that gap is material, the two levers available are renegotiating the reset cycle, moving from monthly to weekly or weekly to a shorter window closes most of the lag, and renegotiating the benchmark lag itself, some formulas apply last week's price, others apply the price from two or three weeks prior, and that difference alone can be the majority of the gap during a fast-moving event. Neither conversation is easy to have mid-contract, but a carrier walking into that conversation with the actual documented dollar gap from the past two months has a considerably stronger position than one arguing from general frustration.

Problem One: The Retail Pricing Gap, Now Worth More Than Ever

The most straightforward way a fleet overpays on fuel is by consistently purchasing at or near retail pump price when discounted network pricing is available. This problem has not changed in nature since March. What has changed is what it costs.

Distribution and marketing costs account for roughly 19 percent of the retail diesel price a fleet pays at the pump, a structural markup that fleets accessing wholesale or cost-plus pricing largely bypass. At the January baseline of $3.52 per gallon, that 19 percent markup on 100,000 annual gallons represented about $66,880 in retail-inflated cost. At today's $6.29 per gallon, the identical calculation, same gallons, same 19 percent structural markup, now represents approximately $119,510. The overpayment did not get worse in percentage terms. It got worse in absolute dollars because the price it is calculated against nearly doubled.

The same scaling applies to the spread between a poorly matched fuel card and a well-matched one. A card delivering 5 cents per gallon at stations your drivers rarely use, against one delivering 40 to 44 cents per gallon at the truck stops they actually frequent, was worth $5,000 to $40,000 to $44,000 annually on 100,000 gallons back in March. That per-gallon spread is denominated in cents, not a percentage of price, so it has not moved with the diesel spike directly. What has moved is the opportunity cost of leaving it uncaptured: in a $3.52 environment, a fleet not optimizing its card program was leaving money on a smaller table. In a $6.29 environment, every fleet's total fuel exposure is roughly 79 percent larger, which means the operational discipline of fixing a mismatched card program now protects a proportionally larger share of total spend.

The volume tier problem described in the original analysis is unchanged in mechanism and more consequential in the current environment. A fleet splitting its fuel spend across two or three card programs to give drivers flexibility may never hit the volume threshold for top-tier rebates on any single program, forfeiting the deepest discounts precisely when the per-gallon savings matter most.

Problem Two: Fuel Fraud and Internal Theft, at a Larger Base

Fuel fraud, card skimming, unauthorized purchases, internal misuse, inflated mileage reporting, remains a percentage-of-spend problem, and that percentage has not changed since March. WEX's research put annual fraud and misallocation losses at 5 to 10 percent of a fleet's fuel consumption, with fraud rates reaching as high as 12 percent in 2024. The National Association of Fleet Administrators estimates fuel theft specifically accounts for up to 6 percent of total fleet fuel cost.

What changes is the dollar exposure sitting behind those percentages. A fleet spending $2 million annually on fuel at the January baseline is now, at current pricing and unchanged gallon volume, spending closer to $3.4 million to move the same freight. A fraud rate of 6 percent against that larger base is a materially larger absolute loss than the same 6 percent was worth six months ago. Fleets that had fraud controls in place before the price spike are now protecting a larger pool of exposure with the same infrastructure. Fleets that had not addressed it are bleeding considerably more than they were in March, without the problem itself having grown at all in percentage terms.

Card skimming incidents, which grew approximately 70 percent year over year from 2022 to 2023, remain the fastest-growing vector, and the higher per-transaction dollar value of every fraudulent purchase in a $6.29 environment makes each individual skimming incident worth more to the person committing it, which is generally understood to increase incentive rather than reduce it.

Problem Three: Passive Operational Waste, Now Costing Real Money Faster

Idling and inefficient driving behavior were always a fuel cost, and they were always somewhat easy to deprioritize when fuel was cheap enough that the waste felt tolerable. That tolerance is gone.

NACFE's research puts a Class 8 truck's idling burn at approximately 0.8 to 1 gallon of diesel per hour. At the January baseline of $3.52 per gallon, a truck idling two hours per day burned through roughly $2,570 in wasted fuel annually. At $6.29 per gallon, that same two hours of daily idling now costs approximately $4,594 per truck per year, a jump of over $2,000 annually from a behavior that has not changed at all. NACFE's broader estimate of $4,000 to $6,000 in annual overnight idling waste per long-haul truck, calculated against the pre-spike price environment, should now be read as $7,150 to $10,740 per truck at current pricing. For a 50-truck fleet with unmanaged overnight idling, that range moves from the original $200,000 to $300,000 estimate to approximately $357,500 to $537,000 annually.

The driver behavior gap documented by NACFE's Fleet Fuel Study, disciplined drivers achieving 7.8 miles per gallon against a national average closer to 6.9, represents the same percentage inefficiency it always did, roughly 13 percent, but that 13 percent is now being multiplied against a fuel bill that is 79 percent larger than it was in January. Telematics-driven fuel savings, documented at an average of 16 percent by Verizon Connect's 2025 survey of 543 fleet managers, are worth proportionally more in absolute dollars today than they were when that survey was conducted.

What the Combined Number Looks Like Now

Rebuilding the 50-truck, 500,000-gallon example from the original analysis at current pricing produces a materially different picture. At $6.29 per gallon, 500,000 annual gallons now costs approximately $3.145 million, up from roughly $1.85 million at the January baseline, an increase of $1.3 million purely from the price environment, for identical operations.

Against that larger base, the retail pricing gap, at a conservative 20 to 35 cent per-gallon spread between a mismatched and well-matched program, is now worth $100,000 to $175,000 annually, unchanged in the cents-per-gallon math but representing a larger share of a fleet that is spending considerably more overall to move the same freight. Fraud and theft, at the NAFA and WEX documented range of 6 to 10 percent of fuel spend, is now worth $188,700 to $314,500 annually against the $3.145 million base, up from $120,000 to $200,000 in the original analysis. Passive operational waste, using the recalculated idling and driving behavior figures above, conservatively adds another $250,000 to $350,000 for a fleet with meaningfully unmanaged idle time and driving discipline.

Combined, conservatively, a 50-truck fleet with all three original problems unaddressed is now looking at $538,700 to $839,500 in annual recoverable fuel spend, up from the $420,000 to $575,000 figure calculated in March. Add the fuel surcharge lag on top of that for any carrier running meaningful contract freight with a slow-reset surcharge formula, and the total exposure for an unmanaged fuel program at current prices is the largest single controllable cost category most mid-size fleets have.

How Trucking Fuel Discounts Actually Work at the Enterprise Level, and Why the Current Environment Changes the Negotiation

Enterprise fuel card programs negotiate volume-based contracts directly with truck stop networks including Love's, TA Petro, and Pilot Flying J, and the depth of discount available to a fleet channeling its full diesel spend through one program has not changed structurally. What has changed is the leverage dynamic in that negotiation right now.

Truck stop networks are also managing a demand environment shaped by the same price shock, and card providers competing for enterprise volume commitments have real incentive to lock in large fleets during a period when total dollar volume per fleet has grown substantially even without any change in gallons. A fleet renewing or renegotiating its fuel program in the current environment is negotiating from a position where its total annual spend commitment is nearly 70 percent larger in dollar terms than it would have quoted a year ago, which is worth recognizing explicitly rather than accepting a renewal at last year's terms.

Your fleet's cost per mile needs to be recalculated with current fuel pricing before any of this negotiation happens. A CPM figure still built on $3.52 diesel is understating your actual cost floor by a wide margin, and accepting freight at rates that made sense against the old number is a direct path to running loads at a loss without realizing it until the numbers catch up at settlement.

The Structural Fix, Updated for the Current Environment

The fix for all three original problems, plus the surcharge lag, is the same integrated approach described in the original analysis, with one addition specific to the current moment.

A fuel card program with volume-based network discounts solves the retail pricing gap. Transaction controls and PIN requirements address fraud and misuse. Telematics integration catches passive waste and idling behavior. How integrated fleet service models reduce fuel costs covers this framework in full, and every part of it is worth more in absolute dollars today than when that analysis was written.

The addition specific to this moment is the surcharge audit described above. It costs nothing to run, takes an afternoon with two months of invoices and the EIA's published weekly archive, and for many contract-heavy carriers it will surface the single largest uncaptured dollar figure of anything covered in this article. Given that the EIA does not expect distillate inventories to normalize before well into 2027, this is not a one-time check. It belongs in the same monthly review cycle as the fuel card and telematics data.

For fleet operators ready to act, fuel card program support that accounts for the current price environment, not last year's, is worth a conversation before the next renewal cycle locks in terms built for a fuel market that no longer exists.

Sources

1. U.S. Energy Information Administration (EIA). Weekly Retail Gasoline and Diesel Prices. Data for week ending September 14, 2026. eia.gov

2. CNBC. Transport Companies Sound Alarm on Skyrocketing Fuel Prices Amid Iran War. September 16, 2026. cnbc.com

3. Axios. Diesel Price Surges to All-Time High, Fueled by Wars. September 2026. axios.com

4. The Conversation. Iran War Pushes Diesel, the Economy's Lifeblood, to Record High Prices, With No Relief on the Horizon. September 2026. theconversation.com

5. Wikipedia. 2026 Iran War Fuel Crisis. en.wikipedia.org

6. Commercial Carrier Journal (CCJ). How the Iran Conflict Is Driving Up Trucking Costs. March 2026. ccjdigital.com

7. Transport Topics. How Fuel Volatility Rewrites Freight Cost Models. April 2026. ttnews.com

8. PBS News. The Iran War and Surging Oil Prices Are Affecting Consumers. Here's How. March 2026. pbs.org

9. Innovative Logistics Group. Diesel Prices Hit $5.37 a Gallon: How the Iran War Is Crushing Trucking Margins in 2026. April 2026. innovativelogisticsgroup.io

10. MVP Logistics. What the War in Iran and Surging Diesel Prices Mean for Your Freight Budget Right Now. April 2026. mvplogistics.com

11. C.H. Robinson. Diesel Fuel Market Update. March 2026. chrobinson.com

12. HaulerMath. Live US Diesel Prices (EIA Weekly Average). Accessed September 2026. haulermath.com

13. Automotive Fleet. Estimated 5-10% of Fleet Dollars Wasted Annually. automotive-fleet.com

14. North American Council for Freight Efficiency (NACFE). Idle Reduction. nacfe.org

15. Verizon Connect. 2025 Fleet Technology Trends Report. Survey of 543 fleet managers. cdn.mediavalet.com

16. Millennials Trucking. Cost Per Mile (CPM) for Trucking: How to Calculate It (with Examples). millennialstrucking.com

17. Millennials Trucking. Why Enterprise Fleets Are Moving to Integrated Fleet Service Models (And What It Saves Them). millennialstrucking.com

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Millennials Trucking covers fleet strategy, fuel management, and operations for mid-size and enterprise trucking operations. Have a topic you want us to cover? Reach out.