mpg on 3.0 and auto lights

[x5-in-uk]

Hello new member from the uk ,my name is john and i imported a 3.0 x5 from usa,i am only getting 16 mpg when driving very carefully and 10 when using mr paddle shifts excellent mod steering wheel.
Also i have the auto light on the car (not standard in uk) and the lights are on all the time,where is the sensor .
Also every time half way through a tank of petrol ses lights up
any help would gratfully recieved