The fuel economy of the soon-to-be released Sonata midsize sedan has been rated at 12.1 kilometers on a liter of gasoline, Hyundai Motor Co. said Monday. South Korea's largest carmaker said that the mileage for the car to be released on the domestic market next week has been rated by the government and reflects numbers for the naturally aspirated 2-liter engine vehicle mated to a six-speed automatic transmission.