When you go to get a new vehicle look at what fuel milage they get
i have driven an 01, 02, 03 and 05 civic and get 40mpg without trying. I actually drive it pretty hard in town but keep a steady 70mph on the freeway. Quite often with my wife and 2 kids, no aero mods. The 05's are dirt cheap but 01-05 is very unreliable and expensive to maintain. My 93 festiva is super cheap to maintain, never breaks down and regularly gets 46mpg driving the same way. They can be bought for $500.
Fuelly is a good place to check real world fuel milage of cars your looking at.