I don't know what to say about your car. Sounds like you just got one that doesn't get good fuel economy, it happens you know. My grandma had two identical 1997 Lincoln Continentals, and the silver one got 3mpg more than the white one on the highway.(with the same person driving the car) The dealer could never find anything wrong with the white one, and the mileage never improved in the entire 30K she put on the car.
On a side note, I recently had a strange experience with my car that I really can't explain. I bought my car in August of 2002 with 12K on it. Since then, I've done mostly city driving, but when I would do some highway driving I only got 25 mpg or so. That was in winter, in summer with the A/C on, I got 21 mpg. I took the car to the dealer, and they couldn't find anything wrong. I just learned to live with it, but it always made me wonder because my Dad's Lincoln got 6 mpg better on the highway. Well, since I've been at school, my car has basically sat in the driveway. When I went to take it back for finals on Monday, it got 34 mpg on the highway. I was truly amazed, and I can't explain the mileage increase.
