US drivers in the Great Lakes region are paying higher prices at the pump after a tornado took Exxon Mobil Corp.'s Joliet, Illinois, refinery offline. A tornado hit transmission lines serving the Joliet plant on July 15, forcing a plant-wide emergency shutdown. The incident has driven West Shore CBOB to a 17.5-cent premium over gasoline futures, according to General Index. That's the biggest premium since November 2022.