It's not easy to change from one engine to another radically different type. I would love for them to go down a path of better fuel economy, torque, weight, and

It's not easy to change from one engine to another radically different type. I would love for them to go down a path of better fuel economy, torque, weight, and horsepower. But you are looking at manufacturers trying to sell cars that need to be serviced down the line. service centers are not trained to handle X technology and the only place you could get it serviced would be the dealership. As a consumer I probably would not want to take the risk of an unknown longevity engine with unknown costs to fix it so I can save 20% on fuel; the engine design must be > 50%-75% less fuel(or some other reason that would make it a no brainer) used to make it worth taking a gamble on unknown quantities.