The U.S. national average for diesel reached a record $6.40 a gallon on Thursday, Sept. 17, while regular gasoline rose to $4.44, according to AAA and U.S. Energy Information Administration data. Gasoline was more than $1.20 above its year-earlier level and had reached a reported national peak of $5.02 on Monday, while diesel had risen 77 cents since the beginning of September. Conflicts involving Iran, Ukraine and Iran-backed Houthi rebels, reduced tanker traffic through the Strait of Hormuz, attacks on Saudi infrastructure, Russia's diesel-export ban and refinery outages constrained crude and refined-fuel supplies. California had the highest gasoline average at $6.09 and diesel averaged $8.35. GasBuddy's Patrick De Haan projected gasoline could reach $4.50 and diesel $6.60 within days, while Tom Kloza of Gulf Oil warned that diesel costs could raise freight, food, utility and heating expenses. The price surge has also become a political issue for the Trump administration ahead of the midterm elections.