In the summer with A/C on I get about 20-22 city. Of course with the A/C on I've gotta give a lot of gas and run the revs a little higher than normal.
In the winter, I enjoy having the A/C off so I just run the revs high and haul ass everywhere for shits and giggles, so I get about 23-25.
Sounds to me likes yours is a little on the low side, but not too far off from mine. I could probably get 18 if I tried.
b