You've got to laugh at the guys cohones

In my experience, it would be fair to tell your dad how many miles the car has done - if thats a genuine story. He can look out for wear and tear issues (like CATS, Bushes etc.) much better if he knows how many miles they've done.

But if you really want to change the mileage I think there are two methods.

You could look out for a second hand set of instruments, but be warned that the red tamper light WILL come one. But your dad may not mind/notice

Apparantly, AND I DONT CONDONE THIS IN ANY WAY, the mileage correction boys (as they call themselves here in the UK), can do it. But they need to reprogram, the cluster, the EWS, the LCM, and the Key. Very messy, and needs someone that really knows what they are doing. No idea what this would cost, it just came up in a converstion we were having down the pub one night. If all of these components aren't updated at the same time, the tamper light will come on (and I don't think it can ever be reset) !

On my E39 535i, this happened when I fitted M5 clocks (to get rid of dead pixels mainly). I documented the cluster change in the service history and the new owner was fully aware of it so the tamper light was just a niusance. I looked into how to get rid of it and thats where the above info came from.

My advice is don't do it. The X5 is good for 250,000 miles (if looked after) so one with six figures on the clock is just really run in.

... (now for the hail or arrows in my direction )

Kev