1156 ET - Casey's General Stores is navigating a choppy fuel environment as rising oil costs weigh on its profitability. "Volatile is the word I would describe the fuel margins," Chief Financial Officer Steve Bramlage says on a call with analysts. "Depending on the headlines that you read about in the paper and social media, there would be a corresponding move in fuel margin over the next day or two." Margins swung from the 30% range to the 60% range during the latest quarter, Bramlage says. Because of the external factors, it has been impossible to solve the problem over the course of a quarter, he says. Casey's shares slide 15%.