I started tracking my MPG in a notebook that I update every time I fill up. My worst mileage - 17.2 MPG averaged over 11 gallons (with an autocross). My best -- 29.1 MPG averaged over 10.8 gallons (all 75-85 MPH freeway cruising).
I have NO complaints about mileage in my WRX. I don't drive like a granny, either.