Admittedly, I don't look under the hood very often ("I'm not that kind of a girl",...lol), but my fan appears to be electronically driven and controlled, however my mileage remains 14/18.
I believe your truck has a mechanical fan for the radiator(attached to a shaft off the front of the engine). I think you also have an electric fan that only operates when the AC compressor is on to pull air through the AC condensor.
Deleting the mechanical fan and adding an electric fan on the radiator would probably help your mpg by at least 1 or maybe 2 mpg. May not be worth the cost of the swap though.