Those are nice looking vans. Do you have the 6 speed with 3.73 gears?
If you bought it new, the mileage will probably improve over the next 20,000 or so. One of the best things I did for my mpg was swap the oem air filter for a K&N....just the filter is all you need. O'reiily has/had them for about $68 best I remember. I gained about 3/4 mpg with just that. I'm told that a good engine tune will increase the mpg by 1-2 mpg also. I haven't done that yet...still under warranty.
Bought it w/ 47,000 on it...going to get the K&n cold air intake...