Iran war pushes diesel – the economy’s lifeblood – to record high prices, with no relief on the horizon
Diesel fuel prices are at all-time highs in the United States. Paul Weaver/SOPA Images/LightRocket via Getty Images Diesel fuel prices in the U.S.
In September 2026, diesel fuel prices in the U.S. reached a historic high of $6.28 per gallon, surpassing previous records. This fuel is critical because it powers freight trucks, farming equipment, construction machinery, and even some heating systems. The surge in prices is driven by three main factors: stricter environmental rules for oil refineries, Russia’s war with Ukraine, and the U.S. war against Iran, which has disrupted shipping routes. Before the Iran war began in February 2026, diesel cost $3.52 per gallon, but prices have since jumped by 78% due to these disruptions. Unlike gasoline, diesel is essential for moving goods across the country, so its rising cost affects everything from food prices to home heating.
U.S. oil refineries have struggled to keep up with diesel demand due to decades of underinvestment and regulatory changes. Starting in 2006, federal rules required refiners to produce ultra-low-sulfur diesel (a cleaner-burning fuel) to reduce pollution. This change cost refiners billions of dollars and reduced their output slightly, as the new fuel contains less energy per gallon. Since 2020, over a dozen refineries have shifted to making renewable diesel (a biofuel) to take advantage of government incentives, further cutting diesel production. In 2025, two refineries shut down, and the remaining ones now operate at nearly 98% capacity—close to their maximum. Despite this, diesel output in August 2026 was lower than in 2025, leaving inventories at their lowest since 1951.
The global diesel market is under strain due to multiple crises. Russia, historically the world’s second-largest diesel exporter, banned exports in July 2026 to prioritize military supplies, extending the ban until the end of 2026 after Ukrainian drone strikes damaged refineries. Middle Eastern refineries, another key source, have also cut production because of the war with Iran. These disruptions have forced the U.S. to export record amounts of diesel to Europe, further depleting domestic stockpiles. By late August 2026, U.S. diesel inventories fell to 103 million barrels, the lowest for that time of year since 1951. The tight supply has left little room for error, and even minor disruptions—like a power outage at an Illinois refinery on September 13, 2026—can worsen shortages.
With diesel supplies scarce, U.S. refinery companies are charging record prices for the fuel. The crack spread—a measure of profit margins for turning crude oil into diesel—surpassed $100 per barrel in August 2026, a first in history. This means refiners are making more money than ever, even as consumers and businesses pay higher costs. For example, the cost of planting major U.S. crops in 2026 rose by $1.4 billion compared to 2025, a 63% increase, with states like Illinois, Iowa, and Minnesota hit hardest. Since nearly all retail goods travel by truck at some point, these higher diesel prices contribute to broader inflation across the economy.
Diesel and *heating oil* (a similar fuel used for home heating) are closely linked, and both are in short supply. The U.S. Energy Information Administration projects that distillate inventories—including diesel and heating oil—will drop below 100 million barrels by September 2026 and stay low through 2027. This is lower than levels seen since 2021, raising concerns for the upcoming winter. Heating oil prices are already up 30% or more, meaning households in the northeastern U.S. will face higher bills. The situation is unlikely to improve quickly, even if the Iran war ends soon, because refineries are running at full capacity with little extra capacity to spare.
