I drive spiritedly on frequent occasion, but also do a lot of highway miles at 75mph. I'm getting 31.2 mpg average.
Did you carry the 1?FWIW, you may want to check your mileage calculations yourself. My car is at least occasionally calculating incorrectly. On my recent trip, it calculated a 99% interstate highway stretch of about 200 miles at 30.6 mpg; my own calculations had it at 34.2 mpg.