No, I haven't miscalculated the figures. I'm averaging 28mpg, and I drive in the "Washington area traffic with plenty of spirited driving"[sightdev's comments]. My mode average is 70mph and I stay in the right lane most of the time--unless passing. My dad owned this car before me and he was averaging 26-33 (mostly highway mileage).
Migirdech:
What makes you think auto-manufacturers make unreasonable mileage ratings on the sticker? The factory drivers are trained to take the most aggressive drivings numbers for the sticker. The average person will range near those figures, and the over-achiever will beat those numbers.
Sightdev:
I agree with your logic, where to get the best gas mileage, but I don't agree with the "miss calculation". Flat land, especially in the Texas Desert helps stabilize, weight dynamics including weight dist., lag, several engine combustions and Latitude, but what most people don't understand is when you press on that throttle, you are leaving a constant speed, and applying more torque--more combustion, and a change in the weight dynamics of the car. There are more factors that apply towards this statement, but I don't have time to go over them.
Just in case you're wondering what makes me an expert on this subject, I am a qualified SCCA and FIA Driver. Experience on the track and in the field makes me an expert.