Increased consumption in X5 3.0d
 

I've done just 60k km in the five years of ownership and for the first time the E53 X5's fuel consumption went to 12.7l/100km after having avereaged 12.2. The only problem I've experienced lately that I think might relate to this is the auxilary heater located under the hood has been coming on every time the car is unlocked.
I spoke with a BMW master tech and according to him, the functions of the auxilary heater is not used in Australia - only required in very cold climates. Replacing this unit will cost US$2600, and if it is not required to function is it worth replacing?
Anyone who can enlighten me whether there would be other reasons for the fuel consumption to go up?
Thanking in advance anticipating feedback :D

The aux heater should not be coming on everytime you lock the car.I simply program mine whenever I want to time it,so you should be able to do the same.
When was the last time you replaced your Air filter?

It was done back in August 2008. I haven't set the auxilary heater to come on. It looks like malfunctioning and I was told it stores the error code. So I hope we should be able to find out some details.

The aux heater would not be able to consume such an amount of fuel that you would see that. Otherwise your cooling water would boil.

If it would start every time you unlock the car, like he mentioned, you bet an extra 0.5l/100km would come up on your OBC.
As about the faulty heater unit, yes, it stores fault codes, but they are more related to failures to start the heater. If you don't have frequent temperatures below 7.5 celsius (if I remember correctly), I would rather disable it then pay the labor and parts for fixing it, which usually are quite expensive.

Yes, I was getting around 730-745km per tank, and the last one I managed just 630km. Which is surprising, gioven that I've average well up to that point.
I think disabling it will be the best rather than pay for something we normally wouldn't use in climatic conditions in Western Australia.
Thank you very much for your posts gents.

Hm, as powers1 said - your air filter - it was changed 2 1/2 years ago? How many km/miles did you drive since then?

I've done 32k km and during this time I've done two oil changes. Thank you.

Might be a good chance to have a look at your air filter. That would be the easiest thing - and of course do something that keeps your heater from starting on it's own during unlocking.

Good luck

Even 12.7 is high for a 3.0d unless all your driving is urban and reasonably aggressive.