Purchased a BMW 730d 5 months ago , disconnected my battery to fix my starter , when i put the battery back the fuel consumption reader goes to zero 0000 , when I started driving the fuel reader keeps on increasing the the nmbrs as i drive to a point of 13L / 100kms , is this normal , before the disconnection the reader was alwys on 8.6L /100 . What could have caused the increase on fuel ? . The fuel consumption seems ok but the numbers is what worries me most , is there any disturbance to the electronics that caused computer systems confused by just disconnecting the battery ???
The reading you had before disconnecting the battery was the cumulated average over many kilometres of driving.
Now you are taking an average based on the few kilometres you have driven since reconnecting the battery, this average is also based on the style of driving and type of trip - so if you are doing short runs with lots of heavy acceleration then the reading seems appropriate.
Take the car for a long motorway cruise and see how the average develops.