Add "NO" as region for this unit. Not sure what "informal" means here. Road signs give distances in km (without writing out the unit). But otherwise the use of "mil" (sometimes with a digit after the decimal marker) is very common for "suitable" distances (driving distances, distance between geographic locations and other distances of that kind of magnitude).
((Plus that "kvadratmil" (square mile-scandinavian) not too uncommon for describing "largish" areas.))