US regulators have announced that Hyundai and Kia have agreed to a record 100 million dollar settlement for overstating the fuel economy of their cars. The South Korean car makers were accused of exaggerating the fuel efficiency of 1.2 million vehicles. According to regulators the penalty is the largest ever paid for violation of the Clean Air Act. The two car makers admitted to having overstated the fuel economy of their cars by up to six miles per gallon. It meant that the companies underreported the cars' greenhouse gas emissions to the US Environmental Protection Agency by around 4.75 million metric tons.As a result, Hyundai and Kai will also be forced to forfeit emissions credits for the difference between the original and the overstated data worth approximately $ 200 million.