A total power outage forced the closure of one of the largest diesel plants in the Midwest, removing 11 million gallons of fuel from daily supply. ExxonMobil's 275,000 bpd Joliet refinery remains offline, contributing to a supply crunch during the peak demand season. This disruption, alongside a partial outage at BP's Whiting refinery in Indiana, pushed US diesel prices to a record $6.45 a gallon on Sept. 18.

National diesel prices have climbed nearly 90% this year and increased 45 cents in the seven days since crossing $6 a gallon. Retailers in the Great Lakes states, including Ohio, Illinois, Wisconsin, Indiana, and Michigan, face high risk of further cost increases. Texas and Oklahoma are the only remaining states with averages below $6 per gallon, at $5.98 and $5.99 respectively.