There are several things that lead to the Prius' excellent gas mileage. 1) It is a hybrid. 2) It is aero- dynamic. 3) They put hard tires on it which are noisy and compromise the ride. and, 4) They use a lot of plastic light weight parts. Some plastic is good, but not in some places.
For instance, they are trying to protect the engine by installing a plastic shield at the underside. While my wife was on vacation this plastic shield came loose and fell off. Before it fell all the way off it dropped down and dragged on the road. The piece was retrieved.
My wife took the car into two different Toyota dealerships and requested to have it put back on under the 36,000 mile bumper to bumper warranty. She was told that it didn't qualify under warranty because the piece was damaged. Instead it would cost us $288 to have a new one put on.
This to me seems a little self serving for Toyota. They put a cheap (expensive) plastic piece on the under carriage of their car. The little plastic rivets holding it on come out. The piece drops down and bangs the highway. And now because it is damaged they won't cover it with their warranty. One of the dealerships said that there have been several of these repairs.
Is this what Toyota has to resort to to make a profit? How can this be a good decision on their part, knowing that their part is faulty, and are willing to displease the customers who buy their cars, for the sake of $288? After this I have determined to buy zero Toyotas in the future. It's not because I don't like their cars, but is the principle. I spend my money on their cars and they screw me on the warranties.
Perhaps they haven't heard that they are no longer the only ones building good cars. Ford Motor is up and coming, and based on my experience with my F-150 I am likely to go that direction with my next vehicle purchase. Who knows, I might even buy a Kia!