Regardless of the kind of car you drive, your driving patterns (primarily your speed) will greatly affect the gas mileage you receive. In the past, studies showed that ~50 miles per hour was the most optimal speed for getting the best mileage. As engines have become more efficient this number has undoubtedly increased. A good rule of thumb these days would be to make sure you don't exceed 60mph and you should get pretty good mileage!
TIP: Keep your driving at 60mph on the highways to optimize your gas mileage .