I was gonna say, km now to miles. but not possible that this entire time you were driving with the digital speedo in km. when the reading is in km, the speed reading is in km.
Here's what you do! Trade your car in for more than you paid for it, because it now has far-far less miles on it! Then, take the proceeds from your sale and get a newer car or upgarde to the "S" (if not an "S" now). Win-win!!