The instanenous speed (+ fuel consumption) was added after your car was built. Yours just won't do it, and that I know of, no one has found an easy and cheap upgrade, but it could exist.
Sorry, but there's lots of other fun things to play with.
Also, most people get used to the center speed after a few weeks anyway, so if you've just gotten the car, you may not care about the digital readout in a bit anyway.
Magic 8-ball was correct. All be in awe of Magic 8 ball.