Diesel fuel in Ventura County hit a record average of $8.06 per gallon on Monday, Sept. 14, according to AAA's Fuel Gauge Survey.
The county's diesel price now exceeds the California statewide average of $7.98 per gallon, which AAA reported on Friday, Sept. 11. The cheapest grade of gasoline in Ventura County averaged about $5.94 per gallon on the same day, KVTA AM 1590 reported.
The record lands during fall harvest season, when Ventura County growers rely heavily on diesel-powered tractors, irrigation pumps and refrigerated trucks. A Joint Economic Committee analysis found U.S. farmers spent about $1.4 billion more on diesel during the 2026 planting season than a year earlier, a 63% increase for major crops, according to Energy News Beat.
Nationally, diesel crossed $6 per gallon for the first time on Friday, Sept. 11, CNN reported. That figure is 60% higher than it was before the U.S.-Iran conflict began in late February, when diesel averaged about $3.76 per gallon, according to AAA data cited by the Insurance Journal.
The price spike traces to disrupted tanker traffic in the Strait of Hormuz, Ukrainian drone strikes on Russian refineries and reduced Chinese diesel exports, according to CNN. California faces an additional squeeze: the state has lost roughly 30% of its refining capacity in five years, including Phillips 66 ceasing crude processing at its Wilmington/Carson facility in late 2025 and Valero idling its Benicia refinery by April 2026, Energy News Beat reported.
California has no inbound refined-product pipeline from the Gulf Coast, according to Energy News Beat. That makes the state structurally dependent on waterborne imports.
Patrick De Haan, head of petroleum analysis at GasBuddy, said in a Thursday, Sept. 10, statement reported by KTVU that diesel powers the freight trucks, agricultural equipment and construction machinery behind nearly everything Americans buy. The costs reach well beyond the transportation sector, he said.
GasBuddy confirmed that six California stations were already selling diesel at the pump display maximum of $9.999 per gallon as of Thursday, Sept. 10, KTVU reported. Forty-seven of 50 states have seen diesel price increases of more than $2 per gallon over the past year, according to De Haan, as Axios reported.
Trucking fleets pass diesel cost increases through fuel surcharges, which then become part of the cost of food, building materials and retail inventory, according to Energy News Beat. De Haan warned in a Wednesday, Sept. 9, statement reported by Fox 61 that record prices "are likely to reignite inflation up and down the supply chain."
He suggested Americans should expect a costlier holiday season as geopolitical tensions continue to drive prices higher.
