First off to the other person who responded ... unleaded is unleaded there is no such thing as better gas = better mileage!
21 miles to the gallon is not horrible but yes it could be better. I am going to guess that you do allot of "city" driving. Lot's of stops and starts and sitting at traffic signals will cut your gas mileage.
Also - Do you let your car idle? When your car is idleing is gets 0 miles to the gallon.
Tips - Start it and go do let the car idle, plan your trips so you are not in heavy traffic, if you can avoid city traffic do it.
Well, if you figure you're probably only using 11-12 gallons, you're looking at 25-27 mpg. That might be a little low for your car, but driving habits and conditions make a big difference.
Reset your trip meter on the dash next time you fill up. Then, when you fill up the time after that, divide the mileage on the trip meter by the number of gallons and then feel all warm and fuzzy for being eco-conscious.
