[knucklebusted]

You can't push a brick through the air efficiently. These things are heavy and have a lot of frontal area. Gas mileage should not be the biggest concern when you buy a truck.

There are only a few things you can do to lower your fuel bill. Foremost is drive less. Second is to lighten your foot. Third is to lighten the truck. After that, it gets real hard to gain much. Clean air filter and properly inflated tires are cheap to do if they are a problem.