The other reason people buy Priuses (or is that Prii?) is that they're more environmentally friendly than the average car. This is largely because of their more efficient use of fuel. With less gas being burned, fewer noxious, polluting emissions are created. And the beltless engine (along with the hybrid drive train) is one of the reasons that less gas is burned. Beltless engines don't waste fuel on anything but making the car move. You can think of environmental friendliness as the flip side of fuel efficiency. A beltless engine provides both more miles per gallon and less damage to the world around you. That's definitely a win-win situation.