Miscalculation of fuel consumption
 

I bought my X3 2.0 d in May 2006 and have suspected that the fuel consumption is measured to low. Since this spring I have put down 15 fill up and the car calculates exactly 1.0 liter (mean) per 10 km less than the actual consumption. BMW says that they can´t see any flaws. Would be very grateful for suggestions how to put this forward with BMW.

All computer averages of fuel consumption tend to be too optimistic. Modern sensors measure the quantity of fuel flow used and come up with an average then. It does not account for the fact that there may still be some fuel "in the pipes", and hence tends to give an average consumption figure lower than the actual amount.

However, it seems like 10 l/100km off, especially in a diesel, may be a sensor problem.

Over my past three BMW vehicles, I have measured actual fuel consumption (several fills, divided by actual km) to confirm the OBC fuel consumption reading. One vehicle was slightly less than 1 litre/100 km off, but the other two were very close.

If you mean 1 litre per 100 km, I wouldn't worry about it. If you mean 10 litres/100 km I would ask the dealer to investigate.

Sorry, of course I meant 1.0 litre/100 km off. I thought the OBC fuel consumption reading would be more accurate.