Aerodynamics of a brick

[dfregozo]

I have my small car that I drive to work and I am getting good mileage. But from time to time I still have to drive my big van that has the aerodynamics of a brick. I set tire pressure at 36 because that is the max on the tires. I did a recent tune up and it is giving 14 street and around 16 highway. It is a 2002 Ford E150 Econoline Conversion van with a high top and has a 4.6L v8. Any tips to make increase mileage? Since its an automatic it limits driving techniques too. I'm afraid that putting the car in neutral a lot will heart the transmission.
The good news is that I drive the van very little, I have my car I drive to work and my wife has her own car, it is just when I drive with the whole family or when we travel that I drive the van.
I'll post a picture shortly.

[gone-ot]

...actually, at highway speeds (55-75 mph) ANY aero mods you can implement become VERY important as drag increases as the square- and HP is increases as the cube-of-velocity!

...hence, the 'easiest' thing to do is simply slow down a little (50-55 mph).