Help needed - Fuel consumption and Mileage query

[robocal]

Hello,

I wonder if anyone can help give me some advice. I am currently in the middle of buying an X5 and today took it for a test drive. It is a 2002 model with very low mileage 17,700 KMS (10,500miles). Although this sounds really low it is not unusual for the part of the world where I live. Anyway after the test drive I decided to check the trip computer for the fuel consumption. It had two readings. One was a stagering 39.5litres per 100kms (7.15mpg) and the other was about 29.5litres per 100kms (9.5mpg). Now being of a suspicious nature I also noticed that some of the LED orange lights that form the letters and digits on the trip computer were not working. So here are my theories / questions ?

1. Could this car have had the mileage rolled back ? Is it possible to do this on an X5 with the digital readout ? It certainly may account for the very high fuel consumption figures on the trip computer.

2. If you cannot roll back the mileage on these cars then can anyone give a reasonable explanation of why the trip computer figures were so outrageously large. Note I did drive the car and it's in beautiful condition and it drives very well.

Anyway any help on this issue would be greatly appreciated