Are you referring to the MCS or the MINI? My '05 MCS with the 6 speed box averages 30.3 MPG over about 7,000 miles, according the the trip computer. Most of my miles are on interstate, however, the computer showing an average speed of about 45 mph.
I drive somewhat conservatively and don't dog the car. Strange, I still seem to treat it like my Triumph, like I'm saving it for something. /ubbthreads/images/graemlins/crazyeyes.gif
The regular MINI gets significantly better mileage. Try one of the MINI websites for detailed info.
The MCS is not an economy car, it's a pure sports car. I'll take the 30+ MPG, it's great for a performance car IMHO.
Good luck with your decision!