In case anyone was wondering what caused the recent price hike, this is one of those rare cases where it's not a mystery.

How 1 Indiana refinery drives up Michigan gas prices
[The problem] occurred this past Saturday, Aug. 8, at BP's refinery in Whiting, Ind., where its largest crude distillation unit — which begins the first step in processing oil — suffered an issue and capacity fell by more than 50 percent....

"Though BP is partially down, they're not making money when they're not selling gasoline. They're losing money."

Reuters reports repairs could take a month or more....

"Because crude oil has been so cheap, refineries have been incentivized to keep producing," [Patrick DeHaan, a GasBuddy senior petroleum analyst,] said. "This is not a time when refineries are deliberately slowing down."
I read somewhere else that it was an unexpected problem with leaking pipes in the initial unit that feeds the rest of the operations at Whiting.