Iowa drivers are paying $.08 below the national average for a gallon of regular unleaded gasoline. Triple A says the cost of gas is $2.43 a gallon. The lowest prices in the state are in Sioux City at $2.31 a gallon, followed by Cedar Rapids at $2.36. Des Moines drivers are paying the most for regular gas at $2.48 a gallon, with the cost in Waterloo ringing-up at $2.43. Gas prices nationwide are down a nickel a gallon from last week.