Louisville-based gas station chain Thorntons is cautioning customers about an impending spike in gas prices.

But the problem is much bigger than one chain or city.

Northern Indiana-based BP Whiting, the largest oil refinery in the Midwest, had a major malfunction on Saturday. And for now, more than half of the refinery is unable to distill crude oil, said Will Speer, a senior petroleum analyst for

That means gas prices are going to increase in the next few weeks.

In Louisville, motorists may contend with a spike of as much as 40 cents — but more likely in the 20-cent range — because of the refinery issue, Speer said. At worst, Louisville prices could reach about $2.70 a gallon, matching the last major spike in the area back in March.

But Speer said relief would come around Labor Day. Refineries will be able to switch to the cheaper winter mixture, and the problems at BP Whiting should be resolved by then, too.

The average price of regular gas in Louisville was $2.47 on Wednesday, according to the AAA Fuel Gauge Report. For context: The price was $3.70 a year ago.