On-road diesel prices climbed into the high $5.60s this week, and according to Aaron Decker, partner and chief executive officer of Multi-Service Fuel Card, the culprit is not crude oil — which has been hovering in the $80s — but a refining capacity crunch that has pushed crack spreads above $100 per barrel, far beyond their typical $15–$25 range. The distinction matters for trucking because diesel is typically one of the largest operating costs for carriers, meaning shifts in refining margins feed through to freight economics more directly than crude price moves alone.

"It's not necessarily a crude issue or a crude crisis," Decker said in a FreightWaves Today interview. "We're not in a crude crisis, we're in a refining crisis."

Ultra-low distillate inventories have fallen to levels not seen since the early 2000s, or even the late 1990s, Decker added — a signal he described as "really troubling." Distillate is the refined-product category that includes diesel and heating oil, so low inventories leave the market with little buffer against refinery outages or demand spikes. That context echoes the tight distillate markets of 2022, when U.S. diesel stocks fell sharply after Russia's invasion of Ukraine upended global refining flows.

Several forces are compounding the supply squeeze. Ukrainian drone strikes have taken out Russian refineries that had previously helped backfill global shortfalls. At the same time, U.S. Gulf Coast refiners have benefited structurally in recent years, with U.S. refining capacity among the world's largest and exports growing since domestic crude export restrictions were lifted in 2015; U.S. Gulf Coast diesel exports are running elevated as domestic refiners supply shortage-stricken markets overseas, which simultaneously tightens American supply and consumes domestic refining capacity.

Decker said the three indicators he watches most closely are a weekly government report tracking Hormuz tanker traffic, Russian refinery runs, and U.S. distillate inventories. The Strait of Hormuz is a key chokepoint for global oil tanker traffic, which is why disruptions there can ripple into refined-product markets worldwide.

"I don't anticipate this getting better in the very near future. I anticipate, and I think the EIA agrees with that, they adjusted their forecast from where they were at the beginning of the year to how things stand now. And I would imagine we're north of $5 for the foreseeable future," Decker said.

He traced the first major fuel-price shock to March 2022, when the Russia-Ukraine conflict erupted, and said geopolitical unrest continues to keep crack spreads elevated. Hurricane season adds another wildcard: El Niño activity could threaten Gulf Coast refining infrastructure in Q3 and Q4, potentially compounding an already tight market. The U.S. Gulf Coast concentrates a large share of national refining capacity, so storm-related outages there have historically amplified price spikes, as seen during hurricanes Harvey in 2017 and Ida in 2021.

On the carrier side, Decker said fleets are leaving money on the table by taking a "set-it-and-forget-it" approach to fuel programs. He also warned that fraud surges when prices spike, making adherence to fraud-protection protocols critical. He urged fleet managers to pull invoices and contact their fuel account managers to uncover savings.

Asked what share of carriers are still paying full retail diesel prices, Decker estimated less than 10% — a figure consistent with roughly 2% cited by a major fuel stop operator during the interview. That means fuel surcharges tied to retail benchmarks may not reflect what most fleets actually pay. For shippers and carriers negotiating freight rates, that gap is worth watching, since surcharge formulas anchored to retail pump prices can diverge from the discounted prices most fleets actually pay at the pump.

Multi-Service Fuel Card, founded in 1978 and credited as the first fuel card to offer real-time transaction authorization for over-the-road trucking, was acquired earlier this year by Decker and two partners, a deal the company announced in May. Decker has been associated with the business since 2012, and the company celebrated its 14th year of his involvement earlier this month.

This summary was generated from a transcription of the interview; the full interview is available in the video above at FreightWaves.