That would do it, stop and go is a killer for gas mileage, rather you have auto start stop or not. It takes a lot of energy to accelerate a SUV. My wife has a lot of stop and go traffic as well on her commute and she is only getting 18 MPG or so, but she has the 35i and has 7000 miles on her car. We also use the on board computer to calculate mileage and seems like you are using the actual figures at each fill up. Your numbers do seem low none the less, does your X3 coast well, and drag at all? Some cars do not get fully break in until 7000 to 8000 miles or so.
Last edited by The X Men; 04-21-2013 at 12:19 PM.