mraldonnelly

"Perhaps it is a very clever system that distinguishes between which key is used to turn on the ignition. The mind boggles"

It is possible for cars to recognise different keys used to open and start cars. One example is the Lexus RX330 built for the Australian market (nearest UK market vehicle is the RX300 which doesn't have as many features) which recognises which key opened the door and sets the seats, mirrors and steering wheel accordingly. Apart from that it is one of the most hateful cars I have ever driven. I think it's ugly, it looks wrong, is a little confused about it's own identity (doesn't do well on the road and certainly wouldn't do well off road), made from some cheap and nasty materials and above all is far too overpriced.

I guess it is therefore possible that your car recognises who the driver is and reverts the trip odo to their setting. Did you try starting the car again with the other key to see if it reverted to the trip in hand?

Andy