The US government has fined South Korean automaker Hyundai and its subsidiary Kia a record $100 million total for misrepresenting the greenhouse gas emissions and fuel economy on 1.2 million cars the companies sold to American customers. The $100 million fine is the largest ever administered under the Clean Air Act, the landmark 1970 law that requires the US Environmental Protection Agency (EPA) to regulate air pollution nationwide.

The EPA found the violations in some of its routine tests of 2012 model Hyundai and Kia cars. After that, the agency conducted further tests, leading it and the Justice Department to filing a complaint. It accuses the automakers of overstating gas mileage by one-to-six miles and understating emissions on six different 2012-2013 car lines total: the Hyundai Accent, Elantra, Veloster and Santa Fe; and the Kia Rio and Soul. As the EPA acknowledges, that includes the majority of the automakers' vehicles for these model years. Not only did Hyundai and Kia's own tests produce inaccurately higher gas mileage and lower emissions, but the companies deliberately chose the most favorable results. In total, the government estimates that Kia and Hyundai's cited cars will produce 4.75 million metric tons more greenhouse gas emissions over their vehicle lifetimes than the companies originally reported.

These cars aren't being recalled, nor discontinued or tweaked in any way, but the companies are publishing updated, correct mileage and emissions estimates, which means that dealers will have to relabel all the affected 2012-2013 cars on their lots. The government is also imposing stricter measures on Hyundai and Kia for the near future. The companies have agreed to revamp their own internal emissions testing groups to prevent violations in upcoming vehicle lines. They've further agreed to have their 2015 and 2016 car models audited. While none of that is going to fix the additional pollution that's coming from the offending vehicles on the roads now, it does send a clear warning sign to automakers that the government can and will force them to pay for environmental lapses.