French auto manufacturer PSA Peugeot Citroen is experimenting with the Hybrid Air, which combines a conventional gasoline engine with a hydraulic drive. This new hybrid will get around 81 miles per gallon in the city, which is much more efficient than existing gasoline-electric hybrids such as the Toyota Prius. PSA Peugeot Citroën says it plans to begin rolling out Hybrid Air cars by 2015 or 2016.