The available Vortec 5.3L V8 offers an impressive combination of 315 horsepower and 335 lb.-ft. of torque and an EPA estimated 21 MPG highway, 15 city when running on gasoline - fuel economy no competitive V8 full-size pickup can beat.(8)
http://www.chevrolet.com/assets/pdf/en/overview/11_Silverado_1500_Catalog_web.pdf