Gas Mileage

[etn160]

A couple of months ago I did a complete tune-up on the Ex. (Changed Fuel Filter, Plugs, Plug Wires, Reset the Computer) and before I did the tune-up I was getting about 20 MPG on the highway. Ever since I have been ranging between 17 to 19.5. The car runs smooth and is not missing or anything. I can't figure out why it would start varying like this. Nothing else has changed.

 

[aldive]

Is it possible that because the truck is running better ( after the tune up ) that you are driving more aggressively? That might explain the decline in gas mileage.