The Environmental Protection Agency has issued a Certificate of Conformity for the Chevrolet Colorado Duramax diesel confirming the Colorado as the most fuel efficient pickup in America. Achieving an estimated 31 mpg highway fuel economy with the two-wheel drive with the Duramax turbo-diesel and 29 mpg for the four-wheel drive diesel, the certificate confirms that with the Colorado’s 21-gallon fuel tank, the 2WD model offers an estimated