Olden, I am in the same boat as you. I just purchased a 2004 Silverado, D/A, crew cab, 4x4, long box and even though I have put few miles on it, I am getting nowhere near the mpg that everyone else has been reporting. So far I have been getting about 13-14mpg totally unloaded highway miles at 75mph. As I have a broken leg right now I have not been able to investigate further(air filter, fuel filter, etc.) What gives?