content: True. Just because the piston-driven combustion engine we have may have reached its limit doesn't mean that better designs aren't out there. Mazda had used the Wankel (rotary) engine for years. One of the American car manufacturers used turbine engines for a few years back in the 50s/60s. While those engines weren't the most fuel-efficient, there are other better designs out there. Car manufacturers need to get off of their asses and look into developing these if they want to keep using gas / diesel to power their cars.