Wankel engine
To improve fuel efficiency further, Mazda is looking at using the Wankel as a range-extender in series-hybrid cars, announcing a prototype, the Mazda2 EV, for press evaluation in November 2013. This configuration improves fuel efficiency and emissions. As a further advantage, running a Wankel engine at a constant speed gives greater engine life. Keeping to a near constant, or narrow band, of revolutions eliminates, or vastly reduces, many of the disadvantages of the Wankel engine.