My yearly mileage is 20,000 kilometers. Mais si vous êtes en France, vous diriez que votre kilométrage est de 12.500 miles (But if you are in France, you would say that your <<kilometrage>> is 12.500 miles).
Because I speak English, but I'm based in a country with a different measuring system. Though mileage refers to the number of miles (per dictionary), I think it's fairly accepted in culture that it's used as a unit of measure for distance covered or to be covered in relation to terrestrial transport methods, when speaking in English. For sea and air, everyone uses nautical miles; how perverse!
I think kilometrage should be added to the English dictionary; it already has garbage, garage, storage, marriage, language...
need I go on?
For the fun of it, German is pretty "easy":
a) Kilometerstand or Tachostand (literally, "kilometer reading, tachometer reading"; meaning: odometer reading)
b) Fahrleistung, Laufleistung (interchangeably, literally "travel performed, distance performed"; meaning: covered distance)
c) Meilenzahl (literally "miles count"; meaning: number of miles, can be used in almost any context, but strictly refers to miles)
d) Kilometergeld (literally "kilometer money"; meaning: allowance for traveling expenses at a certain rate per kilometer)
Meilenzahl is rarely used, not even in translations from English unless it's highly relevant to the story. Now there are some other options, I think the Germans are true perverts when it comes to their language, because they just come up with
bullshit new words every time. Though if one uses Meilenstand (literally, "miles reading"), they'll probably be laughed at: "really? call a friend, 50-50 or ask the crowd?"