The U.S. national average for diesel reached a record $6.505 per gallon, according to AAA, after rising more than 87 cents in September. The increase has been driven by constrained global fuel availability linked to the U.S.-Iran military confrontation, reduced Strait of Hormuz shipments and Russian restrictions on most diesel exports. Diesel is a key operating input for trucking, farming, rail, shipping, backup power and heating, so higher prices are adding pressure across transportation and other industries. The Dow Jones Transportation Average ended Friday 16.1% below its April peak, while companies also face higher borrowing costs as the 10-year Treasury yield nears 5%. Brent crude remained above $100 a barrel, although West Texas Intermediate fell below that level. The Institute for Progress said inflation-adjusted diesel prices remain below their 2022 high, even as nominal prices reached an all-time record. Markets are watching whether diesel prices remain elevated and whether further disruptions affect petroleum supplies.