Audi's R-18 e-Tron diesel-electric hybrid has become the first car of its kind to win the Le Mans 24-hour endurance race. Audi and Toyota both submitted environmentally friendly racers, but the latter's LMP1 crashed, which left the German automaker to a 1-2 finish (while a pair of non-hybrid racers placed third and fifth, respectively). Unlike battery-based hybrids, the R-18 uses a hefty turbo-diesel V6 pushing power to the back wheels, along with a flywheel to recover braking energy and drive a motor attached to the front wheels. The company has revealed that it's actually testing this far cheaper, battery-free system in a production vehicle, so perhaps it's only a matter of time before you'll be able to go a full day on a tank -- give or take the odd rest stop.