Your story reminds me of the time I rented a Renault Twingo in France to do some touring. Nice car other than the fact that it was no bigger than a dining room table and that if you opened up the hood you would swear that there were 2 hampsters running on wheels powering the car. Anyways the speed dial was only in kilometers. I was zipping around doing 145 thinking that was an OK cruising speed. It seemed a bit on the fast side but I just thought it was the effect of being in such a small car. I came home, looked at the speedometer on my truck and realized I was cruising at 90 MPH in that shoebox sized car - no wonder I was getting such bad gas mileage in France.