Human Evolution Explained
it all depends on where you  drive. My 95 XJ gets a bobut 20-22 on the highway, but in the city I get closer to 14 mpg, so due to the amount of city driving i do, I get about 16 average.  The biggest way to waste gas though, is fast acceleration.... that just dumps gas.   If you get a K&N filter(cone filter) and exhaust, you can expect to improve your mileage, because they help the car breath easier, and thus make them more efficient, while adding some power.