FreightWaves SONAR data show retail diesel prices climbing roughly 24% over the past three months while the National Truckload Index, a measure of dry van spot rates, fell about 6% over the same stretch. The chart tracks both series from late June through mid-September 2026.

The gap points to margin pressure for smaller fleets that buy fuel at retail pumps and haul freight in the spot market. The analysis notes that spot rates have not risen enough to absorb the added fuel cost, though the spread by itself does not indicate carriers are losing money.

Larger fleets face a different squeeze. Many buy fuel at a set premium to the wholesale rack price, while their fuel surcharges are tied to slower-moving retail prices. Retail diesel rose about 31% from July 5 to September 17, and wholesale diesel climbed at more than twice that pace. That narrowed the retail-wholesale fuel spread by about 48%.

The spread has averaged just above $1 per gallon since early July, compared with an average of roughly $1.25 from 2022 through March 2026. From April to July, the spread averaged above $1.50 per gallon, which worked in favor of carriers buying at wholesale.

FreightWaves tied the data to the earnings warning issued by J.B. Hunt, which flagged a 5% to 10% headwind in the third quarter from rising fuel and driver costs. Its dedicated and intermodal contracts were priced before the freight market turned in late 2025 and early 2026 and are not renegotiated mid-cycle, leaving the company more exposed to operating-cost swings.

Source: FreightWaves - https://www.freightwaves.com/news/fuel-cost-spike-hits-carrier-margins