http://www.fuelly.com/car/chevrolet...id=125&bodytype_id=&submodel_id=On the home page select browse vehicles. Then input engine and options to get a survey.
I had a 2005 with 5.3, and I got 15 mpg, in rural/highway conditions. My best friend has a 2013, and he said a bit less, but he drives pretty aggressive.
I put 100K on mine, and it was always at the shop. Beside being expensive to maintain it was a nice commuter truck.
