Diesel Spike Erodes Carrier Margins as Wholesale Outpaces Retail

Why did diesel prices hit carrier margins harder this quarter?

Retail diesel climbed 31% from July 5 to September 17, but wholesale diesel rose at more than twice that pace, shrinking the spread between the two by roughly 48%. That compression hits large carriers that buy fuel at wholesale levels, and it hits them before their fuel surcharges catch up. J.B. Hunt issued a rare warning last week that rising fuel and driver costs would shave 5% to 10% off third-quarter earnings.

The problem is timing. Most carriers pass fuel costs to customers through a surcharge pegged to the retail diesel price, which moves slower than the wholesale rack price large fleets actually pay. When wholesale spikes faster than retail, carriers buy fuel at a higher cost than their surcharge has adjusted for yet. That shows up as a narrower fuel spread, which averaged just above $1 per gallon since early July, down from a roughly $1.25 average from 2022 through March 2026.

How the fuel spread works for large fleets

Large carriers negotiate fuel purchases at a discount to retail, but that discount is typically a premium to wholesale. A common structure is rack plus 2%. When the rack price is $3.89, the carrier pays $3.97. Because fuel surcharges are based on the slower-moving retail figure, carriers carry a buffer when fuel costs swing.

That buffer varies with how competitive the pricing environment is and how stable fuel has been. When the market is competitive and fuel is stable, carriers lower base rates, exposing themselves to more fuel volatility. When the market is tight, they raise base rates and reduce long-run exposure to fuel swings.

J.B. Hunt's dedicated and intermodal businesses run on contracts negotiated over much longer terms, and those rates don't get renegotiated mid-cycle. Most of those contracts were set before the market flipped in late 2025 and early 2026. Because those rates were priced competitively to win business in a tight-margin market, J.B. Hunt carries more exposure to operating-cost inflation.

What wholesale volatility means for contract carriers

Wholesale diesel is far more volatile than retail. Retailers buy in bulk and hold prices steadier over time. Wholesale is negotiated daily, closer to a free market. In an inflationary market, wholesale costs rise faster than retail prices, meaning carriers buy fuel at a higher cost than their surcharge has caught up to yet.

The fuel spread from April to July averaged above $1.50 per gallon, meaning carriers benefited. The recent compression to just above $1 per gallon represents margin erosion if fuel surcharge tables and base rates held steady. The market punished J.B. Hunt for what looks like giveback in Q3 from a potentially bloated Q2, not necessarily a long-term threat. Over the long run, carriers that buy at wholesale typically make back the margin loss when fuel prices decline.

The squeeze on small fleets

Small fleets that don't buy fuel at wholesale prices face a different problem. They pay the retail diesel price, which is up roughly 24% over the past three months, while spot rates are down about 6%. That's not necessarily a sign of losing money, but it does point to margin erosion.

The hard part for small carriers is that there's no guarantee they'll recoup that margin loss later. It's entirely market-dependent. As with any commodity, the end consumer will only absorb added cost if they have no other option. Today's market isn't quite that competitive, but it still isn't allowing much further rate inflation.

What this means for a 5-truck fleet

A five-truck fleet running 500 miles per day per truck at 6 miles per gallon burns roughly 417 gallons per day. At a 24% diesel price increase over three months, that's an added $630 per day in fuel cost if diesel was $4.50 in June and $5.58 now. Over a 90-day quarter, that's $56,700 in added fuel expense with no corresponding rate increase to offset it.

If spot rates are down 6% over the same period, the fleet is taking the hit from both sides. A carrier running at $2.00 per mile all-in three months ago is now running at $1.88 per mile with fuel costs up a quarter. The math works only if the fleet was running fat margins in Q2, which most small carriers were not.

Large fleets will likely recover the margin loss when fuel prices decline, assuming wholesale falls faster than retail on the way down. Small fleets have no such structural advantage. They pay retail going up and pay retail going down, and they take whatever the spot market gives them on rate.