it could just be you're seeing lower figures because of the weather....heated seats, heated rear (and front) windows and mirrors and blowers and lights on for every journey all use a huge amount of power, plus starting the car and letting it warm up and melt the ice all eat petrol. I've only been an 8er for a few months but my average is down from 25 to 22 because of all the demisting i am doing. Indeed the handbook says that the rear window heater uses 1 litre of fuel over 10 hrs operation all by itself!
