You should, according to www.fueleconomy.gov be able to get between 19-22 city, and 30 and 32 highway. My mother's subaru outback has the same feature, it will tell you how many MPG you're getting as you drive.
Fuel economy does depend on how you drive...jackrabbit starts and hard braking (slamming them) does decrease your fuel economy. If you're in stop and go traffic, you will be getting significantly less MPG than you would if you were on the open road.
To keep gas mileage up, use cruise control (when road conditions aren't hazardous) and keep a light foot. My mom's subaru shows that when you're coasting...( take you're foot completely off the gas pedal and let the car cruise along at the current speed)...it gets 99.9 miles to the gallon.
Obviously you cant coast all the time, so keep a light foot and don't accelerate too hard. Once you get to the speed you want to travel at, set the cruise control or coast for awhile, or only apply enough pressure to keep the car from slowing down/keep going at constant pace.
Hope this helps!
