The world's gaze has shifted sharply toward the Strait of Hormuz, where geopolitical flashpoints threaten to disrupt crude oil flows. Yet the four-year war in Ukraine continues to exert a quieter, more persistent pressure on global energy markets—one that has now pushed U.S. diesel prices to unprecedented levels. On Friday, the average price of diesel fuel in the United States reached $5.85 per gallon, a record high according to GasBuddy. Regular gasoline also hit a Labor Day weekend record of $4.14 per gallon, surpassing the previous peak set in 2012.

The immediate trigger lies in Ukraine's evolving tactics. Rather than targeting crude oil production or export routes, Kyiv has focused on Russia's refining network with long-range drone strikes. These attacks have knocked out an estimated 40% of Russia's oil-refining capacity, forcing Moscow to cut off diesel exports entirely in July and extend that ban through at least September. The lost output represents about 3% of daily global diesel supplies—a seemingly small fraction, but one that has compounded other disruptions.

Refinery outages have not been limited to Russia. The Middle East has faced its own shutdowns, while China has voluntarily idled some facilities due to reduced oil imports. Together, these factors have taken more than 10% of global refining capacity offline. The result is a market where crude oil remains relatively abundant—thanks in part to the U.S. drawing down its Strategic Petroleum Reserve to 44-year lows—but refined products like diesel are increasingly scarce.

“The Russia situation is really critical,” said Matt Reed, president of the geopolitical and energy consultancy Foreign Reports. “It makes sense that the world’s attention turned to Hormuz since the closure triggered the largest supply shock in history. Yet the real story now is refining constraints that are keeping fuel prices high. When the strait shut, the world tapped crude stocks, but we don’t have the same kind of cushion for refined products.”

Diesel's role as the backbone of the economy amplifies the pain. The farming and trucking industries depend on it, and higher diesel costs ripple through supply chains, raising prices for groceries, household goods, deliveries, and countless other products. “Diesel is the fuel that moves the economy,” said Patrick De Haan, head of petroleum analysis at GasBuddy. “When diesel prices reach record levels, the impact extends far beyond the transportation sector.”

North American refineries have tried to fill the gap by running at maximum capacity, generating record profits. But the seasonal shift is approaching: many refineries plan to undergo maintenance in September and October, switching to winter-grade fuel. While some have delayed those plans, others—including Canada’s largest refinery near Maine and several Gulf Coast facilities—will still reduce output. Gregory Brew, senior energy analyst at the Eurasia Group, predicted that the diesel shortage will persist. “That’s going to put even more pressure on product prices in the U.S.,” he told Fortune. “And that’s likely to come in mid-September and it’s going to last through November.”

Russia’s domestic fuel situation is even more dire. The country has been forced to import gasoline from Kazakhstan and refine some of its own crude in Kazakh facilities, further straining global supplies. The success of Ukraine’s drone strikes reflects a shift in the balance of air defense. “What’s changed is how much success they’ve had at hitting their targets,” Brew said. “That suggests that Russian air defenses have been slowly whittled down. The Russians can’t shoot down Ukrainian drones and missiles with the same kind of effectiveness of a year ago. The Ukrainians are having more success hitting refineries, including around Moscow.”

Ukraine's strategy has evolved from scattered attacks on pipelines, tankers, and platforms to a concentrated assault on refineries—large, stationary targets that are difficult to repair quickly. The disruptions have spread beyond the war zone. Russia’s Nord Stream pipelines were sabotaged in 2022, Ukraine has struck the Druzhba pipeline system, and periodic interruptions have hit Kazakhstan’s oil production via the Caspian Pipeline Consortium. NATO recently shot down a drone near Romania’s Black Sea gas projects. Yet crude oil and natural gas markets have largely adapted, thanks to reserves and renewable energy growth. The refining system, however, has no such buffer.

“We’re seeing increasing tightness for refined products,” Brew explained. “Diesel in particular is going up across the board in lots of different markets and that is, to a great extent, downstream of what Ukraine has been doing against Russia.” He added that while Ukraine may not be winning the war overall, its attacks on energy infrastructure are causing Russia more economic pain and generating global ripple effects. “Where the balance is shifting more in their favor is this war against Russian energy. The Russians are having an increasingly hard time defending their domestic infrastructure. It’s affecting the global energy market, and it might be compelling Russia toward pathways of escalation to improve the status quo in their favor.”