Strange behaviour of Service Indicater

[BARRIE]

I am a little concerned as to the behaviour of the Service Interval Indicater on my Tdi 45. When I bought the car at 22000 miles 3months ago it indicated service required in 6000 miles. I have used the car for long distance commuting over the last 3 months, 50miles each way. The Indicater now says service in 9200 miles. Two weeks ago it said service in 9100 miles.
Does anybody know how this indicater works? What type of Sensers does it use to determine oil condition , and should I be concerned at the somewhat erratic backward progression of the indicater?
PS I am averaging 62.8 mpg over all but mostly cruising at 50 - 70mph .
Regards,
Barrie

[ULP]

Perfectly normal.

Before you bought the car it may have been sat around not being used, or going on small test drives; somebody may have been using it for short journies and the varible servicing would bring them in very quickly. Now it is adapting to your driving style.

My A2 was a demo and when I bought it with 2950 miles on the clock the service indicator showed 6500 miles - within a few thousand miles it was up to 9000 miles 'till service and then dropped slowly; I got to 21500 miles before it called me in for the service! I am now looking at getting 25,000 miles to the second service.

[BARRIE]

Many thanks for reassurance ULP. I would like to find out a little bit more about the nuts bolts and electronics of how this service indicatoe actually works. Also and related to this, I think there is a market for an add on fuel consumption meter for cars not equipped with trip computers. I have a history of making breakthroughs on seemingly difficult projects so watch this space!
Regards,
Barrie

[erstens]

The indicator updates only every 500km and it will show zero after two years! So it will be the time factor as said before.