U.S. oil has its biggest one-day price increase in six years

Stocks swung sharply, and the average cost of gas nationwide hit $4.08 a gallon for unleaded and $5.51 for diesel.

Oil prices surged Thursday, threatening to further drive up the price of gas as hopes for a near-term resolution to the Iran war faded following President Donald Trump’s address to the nation.

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Stocks were volatile, with major indexes plunging early in the day before moving higher at the close on shifting headlines about the war in the Middle East.

U.S. indexes recovered their early losses on news that Iran’s deputy foreign minister said his country would outline a "new navigation regime" in the Strait of Hormuz after the war ended, injecting fresh optimism into markets over the future of the key waterway.