I'm amused to see that (so far) no-one has said that they think exclusively in kilometres. I've fairly often come across fanfic written by American writers, in which they very carefully have all their British characters measure distance in kilometres, since they've read that Britain has officially gone metric. The writers do, of course, deserve top marks for trying to ensure that they use terminology that suits their characters (some writers don't bother), but it's slightly unfortunate that in this case they're... well, er... wrong.