Hi Brid,

We’re not sure which year C5 you’ve got, but there should be a MENU button on your centre stack. Press it to bring up a range of items on the display, one of which should be UNITS. This can be cycled between l/100km and mpg, and this will also switch the other digital displays to km/h and mph accordingly. If it’s a newer C5, try the left-hand steering wheel-mounted thumb wheel briefly, then in the instrument cluster scroll down to UNITS and you can do the same change.