This questions does my head in, someone asked me it a while ago and I don't feel like it was answered right. If you have a car, travelling at 60mph and it used its full tank of fuel. This means on a very long straight road it would cover 60miles on the hour with no fuel left. Now, providing everything stayed the same, gears, speed the axel is spinning, and the time of an hour, the car would surely travel further if the wheels we swapped for a larger size. Say tractor wheels. Much larger wheels means further to go before it completes one rotation, so it would cover more ground on the same amount of fuel.? Why aren't we driving around with tractor wheels and saving fuel? would kick *** in winter.