Diesel fuel prices have surged past $5.40 a gallon, hitting record seasonal highs in mid-August as tensions between the United States and Iran intensify over control of the Strait of Hormuz. Drivers are paying an average of $4 a gallon for gasoline and $5.40 for diesel in the second week of August for the first time, according to AAA data, as a 60-day ceasefire between Washington and Tehran expired on Monday with no end to the conflict in sight.
The spike in diesel fuel prices reflects a year-long surge driven by geopolitical conflict in the Middle East. On-highway diesel prices rose from $3.48 to $5.35 per gallon between early January and early August 2026, a 53.8 percent increase, according to transportation cost analysis. The latest jump follows the expiration of the US-Iran ceasefire, which had been signed in June, prompting oil markets to price in renewed supply disruption risks.
The Strait of Hormuz remains at the center of price pressures. The waterway handles about one-fifth of global daily oil supply, according to Reuters reporting, and has been a flashpoint in the US-Iran conflict. On Monday, when the ceasefire expired, Iran said it would adopt a “fully offensive” military stance, and just six cargo ships transited the strait on that day, according to ship tracking company Kpler. A cargo ship was attacked while traveling through the strait early on Tuesday, according to the UK Maritime Trade Operations agency.
Oil prices climbed sharply in response. Brent crude rose above $90 a barrel for the first time since July 30, trading at $91.63 on Tuesday morning, according to The Guardian. Analysts at Deutsche Bank wrote that rising oil prices signaled investors pricing in “a more extended closure” of the strait. Angeline Ong, a senior technical analyst at the investing platform IG, warned that President Trump’s threat to bomb Oman if it interferes with US efforts could be a turning point. “Trump’s threat to bomb Oman could be the moment the oil market shifts from pricing a temporary disruption to pricing a prolonged one,” Ong said, noting that “roughly a quarter of global seaborne oil normally passing through the strait” means even a small reduction in reopening probability warrants higher geopolitical premiums in crude.
The trucking industry faces sustained pressure from elevated diesel costs. Fuel remains one of the largest expenses for trucking companies, and higher prices directly squeeze profitability for owner-operators and fleets. The Department of Energy forecasts that diesel prices will fall to just under $5 by the end of 2026, but that figure remains well above seasonal norms. Gasoline inventories in the U.S. are at their lowest level since November 2025, according to government data released August 12, with some regions such as New York and New Jersey at their lowest since November 2024.
The current price environment represents a continuation of the spike that began when the US-Israel war on Iran escalated in February 2026. When that conflict first erupted, diesel prices surged by more than 40 percent in under two months, according to reporting from April 2026. The latest ceasefire expiration and renewed tensions show the market remains highly sensitive to Middle East developments. Dan Alamariu, chief geopolitical strategist at Alpine Macro, warned that without an end to Middle East fighting, energy prices could face a “double whammy” when combined with Russia’s ongoing war in Ukraine, with escalation from September through November likely to deliver sustained pressure on oil and gas markets.
Sources
- Transport Topics — record August diesel and gasoline prices, AAA data, Department of Energy forecasts
- The Guardian — ceasefire expiration, Brent crude prices, analyst commentary from Angeline Ong and Dan Alamariu
- Reuters — Strait of Hormuz oil supply share, ship transit data
- True Driving Cost — year-to-date diesel price increase percentage
- Quartz — record seasonal high diesel prices
