US diesel price hits record $5.85 a gallon, AAA says

US diesel prices rose to a record $5.85 a gallon on Friday, up from $3.71 a year earlier, the AAA motorists' association said, as the US war with Iran continued to disrupt energy markets.

Diesel is a key fuel for road hauling, agriculture and construction. Farmers use it to run equipment, and trucks use it to move food to grocery stores.

The increase comes weeks before November's US midterm elections, with voters also facing persistent inflation. North Carolina farmer Derrick Austin told AFP that higher diesel costs could add about $15,000 to his fall harvest of soybeans and corn.

Austin said farmers were growing frustrated with President Donald Trump's administration, though he said it was unclear whether economic concerns alone would push voters away from the Republican Party.

Afdhal Rahman of banking group OCBC said in a recent note that prices for refined products such as gasoline and diesel had risen meaningfully and outpaced the increase in crude oil prices, even as oil prices largely hovered around $90.

Prices at the pump have risen since US-Israeli strikes targeting Iran from late February sparked Tehran's retaliation in blocking the Strait of Hormuz, a key waterway for energy transit. Global oil prices have remained high and rose this week after a fresh escalation in fighting.

US farmers also faced higher fertilizer and diesel costs as the spring planting season began. Austin said he was concerned fertilizer costs would stay inflated until next year because of the blockage of Hormuz.

The Independent Grocers Alliance estimates that fuel-related costs can account for 15 to 30 percent of the total cost of some food products.

Regular gasoline is also higher, with the US average at $4.15 a gallon, compared with $3.20 last year.

US Vice President JD Vance blamed Iran when asked about earlier comments by Treasury Secretary Scott Bessent that Americans could potentially see $3 gasoline again by Labor Day, which falls on September 7. Vance said fuel prices were inherently unpredictable and also criticised Europe for being unable to keep markets supplied.