US petrol prices have surged 42% since the Iran war began in late February, the sharpest increase among G7 nations, according to JPMorgan. Average pump prices hit $4.39 per gallon on Friday—the highest since Russia's 2022 invasion of Ukraine—up from $2.98 prewar. California motorists are paying $6.06 a gallon.

Canada and the UK recorded the next highest increases at 24% and 19% respectively, while Italy saw just a 4.6% rise. The steeper US increase reflects lower fuel taxes compared to European nations, where governments have introduced subsidies to cushion consumers from price shocks. "In the US it's the consumer bearing the cost, whereas in other countries the state is doing more to absorb the additional cost," said Edward Hayden-Briffett at The Officials. US exports to Asia are also draining inventories during peak demand ahead of the summer driving season.

Diesel prices—critical for US industry—have jumped 48% to $5.57, nearing record highs. Trump's approval rating fell to 34% this week, the lowest of his term. ExxonMobil and Chevron said they won't increase production beyond existing plans despite higher oil prices. Industry observers warn the administration may face calls to restrict exports if prices stay elevated through Memorial Day weekend.