I've had 17.8 l on my 18i for urban driving in winter conditions. Now the Board Computer shows like 14.5 l per 100 km. However, I suggest you not rely on this indicator.
Worth noting that I rarely spin the engine over 4,000 rpms.
I'd rather open service menu (to open the menu, press the trip odometer reset button and, while holding it, insert the key) and check entire mileage / consumption collected by the car for the entire driving period since the last time when your battery was discharged.