U.S. motorists could see higher gas prices in the coming months as major refineries shut down for repairs, according to The Wall Street Journal.

Cheap gasoline has spurred more driving and more demand for fuel.

Last week, U.S. refineries processed around 17 million barrels of crude a day, according to the federal Energy Information Administration. That’s 540,000 barrels a day more than refineries handled a year ago.

Refineries are operating at near capacity and any interruption can result in a price spike, John Auers, a refinery consultant at Turner, Mason & Co., told the Journal.