Discussions in Washington regarding a potential ban on the export of American diesel fuel are currently transforming global oil markets. The most obvious sign of this influence is the change in the spread between US crude oil futures and the international Brent benchmark. Traders suggest that if American refineries have to store more diesel fuel domestically, they will generally process less crude oil, which has led West Texas Intermediate to trade $12 per barrel lower than Brent, the widest discount since early May.
The catalyst for this situation was a crisis in fuel pricing that had been building up for months. According to AAA data, diesel prices in the US reached a record $6.52 per gallon this week. This prompted President Trump at the UN General Assembly to declare his support for keeping diesel supplies within the country rather than sending them abroad. Treasury Secretary Scott Bessent confirmed that officials are studying the possibility of imposing a full or partial export restriction. However, the White House then introduced uncertainty by refuting reports of an imminent 90-day ban, while Energy Secretary Chris Wright insisted that a comprehensive ban was not being seriously considered.
This uncertainty has not stopped the market from factoring in the possibility of such a ban. Analysts at Wood Mackenzie estimate that a ban could redirect about 700,000 barrels per day of surplus diesel and gas oil to domestic storage, allowing Gulf Coast reserves to fill in less than a month. Furthermore, it would force refiners to cut crude oil processing by more than two million barrels per day, representing about 12% of current processing capacity in the US. Considering that America exports approximately 1.2 million barrels of diesel fuel per day out of a total production of 5.1 million barrels, according to Morgan Stanley, the scale of the disruption to refinery economic activity will be significant.
The consequences are already being felt far beyond the US. The premium on diesel fuel in Europe relative to Brent crude, known as the pricing gap, jumped above $95 per barrel this week, a record according to data covering the period up to 2011, as a leading external supplier signaled a possible flow restriction. Citi analysts warned that any restriction by the US could further narrow global supply while giving an advantage to Asian refineries that will remain to absorb the load.
Refining company stocks have also suffered. Valero, Marathon Petroleum, and Phillips 66 traded down during the week, despite their underlying margins remaining historically high; for example, Valero's Gulf Coast diesel margin has roughly tripled year-over-year. Energy economist Philip Verleger cautioned that a ban could damage America's long-term position as a fuel exporter, comparing the potential consequences to the soybean embargo of 1973 under President Nixon, after which buyers permanently redirected their purchases elsewhere.
The situation is complicated by separate pressure on shipping. The war with Iran has led to a sharp rise in freight rates and reduced vessel availability, weakening the usual logic of arbitrage, which dictates that widening the WTI-Brent spread should stimulate greater exports from the US. Freight analysts at Signal Maritime note that transporting crude oil from the US Gulf Coast to Asia now costs approximately $50 million per voyage on a very large tanker, roughly three times the pre-war level. Even though WTI trades with a steady discount of $4 or more to Brent since July, crude oil exports from the US have barely changed, increasing by only 45,000 barrels per day between July and August, and are forecast to fall for the third consecutive month in September.
As one trader noted, a wide paper spread is an invitation to test arbitrage, not proof that it is actually open. Given the political urgency added by the November midterm elections and the absence of formally signed policy, the coming weeks will likely test how far the crude oil and diesel markets can diverge before something happens—either at the pump, in refinery margins, or in Washington's political calculus.