Lots of auto brands are concerned with "greening" themselves these days, but not all of them have the "street cred" to back those statements up. Kia, on the other hand, has the full support of the EPA. According to a 2011 EPA Fuel Economy Trends Report, Kia boasts the largest gains in fuel economy in the industry- along with the greatest reduction in CO₂ emissions. According to the survey, Kia "had the biggest improvement…