Haha, I've seen this one in action!
See, we had to limp Star's car 200 miles or so on a very bad road, and one of those 'donut' tires. Normally the tank would've been empty by that point, but there was still quite a bit of fuel left. We were driving about 55, accelerating and braking veeeeery carefully... the saved gas was about the only upside of that day.