umm... the tire argument is invalid since car manufacturers actually provide certain tire specifications with their cars which as a side reason is for keeping the speedometer in a certain tolerance of accuracy.
And no, when you go 40MPH than you do less then a mile per minute. The question is specificly about "you go x MPH" and not about "you accelerate to x MPH". If there is no acceleration or deceleration then you do a constant speed and speed is per definition way per time.