[Tannaton]

You can use a car in km in the UK - every model I have seen has the alternative units also marked on the speedo.

The mileage is stored in the instrument cluster and it is possible to alter this, it’s is also stored in the central electronic module (CEM) and I don’t think it’s is possible to change this in isolation?

FYI the CEM is configured at the factory for miles or km and the distance is also stored in the native unit, and service reminders, speed limiter etc is based in those units.

So as Clan said if you a really determined to do this then a full software reload of all relevant modules would be the only safe, predictable way. Whether Volvo has a documented process for that I don’t know, if they don’t then I suggest it’s not an option.

A safer option might be to buy a second hand instrument cluster and swap all the guts of yours into it - if the speedo was on the same scale. You’re odometer would still be in km but speed readout in mph. I’m sure there will probably be a downside to this but I can’t think of one currently.