hey everyone! I just bought a 2010 2500 with the 6.0 and im pretty disappointed in the fuel mileage. I bought the truck with the notion that it would be getting around 15mpg. This coming from guys that have similiar trucks and the not so trustworthy salesman. In reality the best ive seen is 12.5 and that was on the interstate unloaded at 70mph. Its stock aside from a set of aftermarket 17 inch wheels. Im wondering if anyone has advice on how to up my mileage and or horsepower? My local performance shop says its a lost cause and that I should have went back to the duramax. But I had a hard time justifying the extra ten grand when I dont pull every day. Id really appreciate any help I can get!!