2012 Gmc sierra 2500 denali gas mileage Read Also: 2008 Gmc sierra 2500 diesel gas mileage 2013 Gmc sierra 2500 denali review 2003 Gmc sierra 2500 diesel gas mileage 2500 Gmc sierra denali Gmc sierra 2500 duramax mileage 2008 Gmc sierra 2500 gas mileage