Is it new car it may have a system which regonises the type of driving or a may just be faulty the 307 which I am using at the moment which has the same electrics as the older C3 counts down to zero.Try reseting the counter and see what happens.

dropped about 300 miles when I've only driven about 40 this week.

I think variable service indicators give a heavy weighting to short journeys. Also there's a time interval, so the counter will drop even if you don't drive.

The "miles to service" is a straight countdown, and is reset at the service.

There was a fault with this system on Citroens around 2006-2008, but IIRC a software update fixed it.

Edited by BigJohnD on 04/03/2013 at 17:47