2008 Gmc sierra denali fuel mileage Read Also: 2007 Gmc sierra denali fuel mileage 2008 Gmc sierra 1500 denali fuel economy Improve gas mileage 2008 gmc sierra 2008 Gmc yukon denali fuel mileage 2007 Gmc sierra fuel mileage 2008 Gmc denali truck gas mileage