U.S. diesel prices climbed above $6 a gallon for the first time Friday, as disruptions tied to the war with Iran and Ukrainian attacks on Russian energy infrastructure tightened global supplies of the fuel that powers much of the country's trucking, agriculture and industrial economy.
The national average for diesel reached a record $6.0556 a gallon on Sept. 11, according to AAA, up from $3.7053 a year earlier and $5.3213 a month ago. Regular gasoline averaged $4.2950 a gallon, compared with $3.1949 a year earlier.
The diesel increase has been particularly sharp since the U.S.-Israel war with Iran began in late February. Reuters reported that diesel prices have risen nearly 60% since the conflict started, while U.S. diesel inventories are 13% below their five-year average.
Crude prices have also returned above $100 a barrel. Brent crude traded around $104 Friday after settling at $107.63 a barrel Thursday, while West Texas Intermediate had settled at $102.48, as attacks on tankers and energy infrastructure disrupted oil flows from the Middle East.
The strain is extending beyond crude oil into refined products. Diesel is widely used in freight transportation, farming and industrial operations, meaning changes in its price can increase operating expenses for businesses that move goods or depend on heavy machinery.
The U.S. Energy Information Administration this week raised its outlook for diesel prices. It now expects retail diesel to average $4.40 a gallon in 2027, an 8.2% increase from its previous forecast of $4.07.
For the fourth quarter of 2026, the EIA expects diesel to average $5.55 a gallon. The agency also forecasts U.S. distillate inventories, which include diesel and heating oil, will fall below 100 million barrels in October for the first time since 2003 and remain below the five-year seasonal low through the first quarter of 2027.
The EIA's September forecast was completed using market information available through Sept. 3 and therefore doesn't incorporate the latest increase in oil and diesel prices. Its current outlook assumes Middle Eastern crude production will gradually recover, with most output returning near prewar averages by the second quarter of 2027.
Russia has added another source of pressure. Ukrainian attacks on Russian refineries and other energy infrastructure have reduced production and fuel availability, while restrictions on Russian exports have further constrained refined-product supplies. The International Energy Agency on Friday cut its Russian oil-production forecasts for both 2026 and 2027, citing continuing Ukrainian attacks.
Higher pump prices have already imposed substantial additional costs on U.S. consumers, according to researchers at Brown University. The university's Climate Solutions Lab estimated that cumulative extra gasoline and diesel spending since the Iran war began Feb. 28 surpassed $100 billion on Sept. 7 compared with a modeled scenario in which the war hadn't occurred.
Brown estimated that the average American household had paid more than $750 in additional gasoline and diesel costs by early September. The researchers calculate the burden by comparing actual AAA fuel prices with a counterfactual price trajectory based on prewar prices and historical daily changes, then combining the difference with EIA fuel-consumption data and Census Bureau household figures.
The estimate has increased rapidly as the conflict has continued. Brown's researchers calculated in mid-April that the additional nationwide fuel cost had reached roughly $20 billion, equivalent to more than $150 per household. By May 18, the figure had exceeded $40 billion, or more than $300 per household.
The rise in fuel prices comes less than two months before the November midterm elections, placing energy costs alongside other affordability issues in the political debate. Brown's Sept. 8 research brief noted that the response of voters to higher energy costs remains uncertain.
President Donald Trump has defended the U.S. military campaign against Iran despite the increase in energy prices. Meanwhile, supply disruptions have continued: Saudi Arabian crude production fell to about six million barrels a day in August, its lowest level in more than three decades, while shipping through key Middle Eastern routes has faced repeated disruptions from attacks on vessels and energy infrastructure.
The EIA estimates global oil inventories have fallen by roughly 400 million barrels so far this year. Its September outlook expects inventories to continue declining through the end of 2026 before rebuilding as Middle Eastern production recovers during 2027.
