If this car came with a cat converter and 5 wire O2 sensor, like it was supposed to, it would have given comparable results to a City. Even with this design, you could still reduce the fuel consumption with your driving style. First of all, get its air/fuel ratio adjusted; it has probably never been adjusted by the previous owner.
You will have to learn some fuel saving techniques for automatic cars. One of them is the rate of acceleration. Find out the minimum shift speeds and torque converter lock up ranges. In my '03 VTi, the minimum shift speeds are: first to second at 1800 rpm, 2nd to 3rd at 32 km/h, which is where the torque also locks up. The car will slowly accelerate to 50 km/h like this.
If you want to go faster than 50, press just enough accelerator to unlock the converter. At about 60 km/h, momentarily let go of the accelerator; this will make the transmission shift to fourth and lock up. In my experience, it stays in lock up at or above 60 km/h, but it will unlock with the slightest hint of a heavy foot. If you want to go even faster, unlock the tq again (don't let it downshift); release the race and then press it again to lock the tq.
-keep the rpm between 1500 and 2500
-keep the transmission in lockup as much as possible