The other thing, in a car like a BMW, you hardly "feel" like you're doing that speed (well, we went up to 112mph / 180kph). In a more average car, you can do it as well, but you'll feel it shaking and you get a much stronger feeling of "wow I'm going really fast" (which is kinda unnerving IMO). It's a complete waste of gas either way, of course (110 kph generally gives the most kilometers for your litre, in most types of cars, I've found).