How the U.S.–Iran War Reshaped Oil Markets—and Why the Buffer Is Running Out

Seven months into the U.S.–Iran war, the oil market is functioning on contingency measures rather than a durable replacement for disrupted Middle Eastern exports. Some barrels have been rerouted, producers in the Americas have increased exports, and governments have released emergency oil. Yet the cost of keeping the system supplied has been a rapid drawdown in inventories—and that leaves prices and the wider economy more vulnerable to further attacks or shipping interruptions. 119

The shock was driven by both lost supply and blocked transport

Middle Eastern exports accounted for roughly one-fifth of global oil supplies before the war. Early in the conflict, the International Energy Agency estimated that around 11 million barrels per day of supply had been removed; later estimates of the ongoing Gulf disruption varied, reflecting uncertainty over production, transit and covert shipments. By late August, analysts cited by Reuters put the continuing disruption at roughly 5 million to 7 million barrels per day. 93

The Strait of Hormuz is the decisive bottleneck. Before the conflict, an estimated 21.6 million barrels per day moved through the waterway; second-quarter flows fell to 4.9 million barrels per day, according to U.S. estimates reported by Bloomberg. 7 This distinction matters: oil that can be produced but cannot be loaded, insured or safely transported does not fully reach the world market.

Saudi Arabia has rerouted oil toward the Red Sea, while some Gulf exports have moved through alternative ports and exceptional shipping arrangements. Those measures have eased the immediate shock, but they have not restored normal trade flows. Reuters reported that Gulf exports remained well below the roughly 18 million barrels per day that passed through Hormuz before the war. 3

Why prices rose even as the market kept receiving barrels

Oil prices reflect both available physical supply and the risk that future deliveries will fail. Renewed U.S.–Iran military exchanges in September lifted crude prices and coincided with record U.S. retail diesel prices, Reuters reported. The pricing pressure is therefore not just about barrels already missing from the market; it also captures disrupted freight, insurance and the prospect of further damage to energy infrastructure or shipping lanes.

That is the fragile “new normal”: a market in which flows continue, but at higher cost and with much less redundancy. A disruption to a pipeline, port, tanker route or refinery can have an outsized effect because the principal alternative routes are already carrying more of the load.

What has kept the market from a deeper crisis

Three buffers have softened the loss of reliable Middle Eastern supply:

• More crude from the Americas. Exports from the Americas averaged a record 11.7 million barrels per day in 2026 through early September, up from 10.3 million barrels per day in 2025. The United States led the increase, followed by Brazil, with Asia absorbing much of the additional supply. 2
• Rerouting and alternative export capacity. Saudi Red Sea exports and other alternative-port flows have provided an outlet for some Gulf crude that would otherwise depend on Hormuz. 311
• Emergency stock releases and lower consumption. All 32 IEA members agreed to a record 400 million-barrel release from strategic reserves early in the conflict. Higher prices and weaker economic activity can also curb fuel use, reducing the immediate gap between supply and demand. 18

These responses have bought time. They have not recreated the lost combination of dependable production, low-risk shipping and ample inventories that existed before the conflict.

The key trade-off: the world is consuming its oil buffer

The clearest sign of the market’s strain is inventory depletion. The IEA said global observed oil stocks had fallen by about 507 million barrels since the war began, an average draw of roughly 2.8 million barrels per day; August alone saw a 95 million-barrel decline. 1914

The U.S. Energy Information Administration separately reported that global inventories had fallen by about 400 million barrels so far in 2026 and expected further declines through year-end. Different measures and time periods can produce different totals, but both point to the same conclusion: stored oil has been covering a material share of the shortfall. 8

Strategic reserves are designed for this kind of disruption, but they are finite. Reuters reported that the U.S. Strategic Petroleum Reserve stood at 289.7 million barrels in early September, its lowest level since 1982. 17 Releasing stocks can cushion a temporary interruption; it cannot indefinitely replace a persistent multi-million-barrel-per-day loss.

Why the next phase may be harder than the first

The IEA’s September outlook projected a 5.7 million-barrel-per-day decline in global oil supply for 2026 and delayed a full recovery in Gulf supply until 2027. 1 That outlook means the market’s resilience will increasingly depend on whether alternative routes remain operational, incremental non-Gulf supply continues to arrive, and demand weakens enough to match constrained availability.

For consumers and businesses, the exposure extends beyond crude prices. Costlier or less reliable oil flows can lift transport and refined-product costs, which can feed into broader inflation pressures. The market has absorbed an extraordinary shock so far, but it has done so by spending down the very inventories that make future shocks manageable.

Bottom line

The war has not created a stable replacement for disrupted Middle Eastern supply. It has created a stopgap system built on rerouted barrels, record exports from the Americas, emergency reserves and lower demand. With global stocks already down about 507 million barrels and normal Gulf flows not expected to fully recover until 2027, the oil market remains highly exposed to another escalation. 191