If you like your Audis on the sporty side, just swap the A for an S. That mantra holds true for Audi's flagship sedan, the A8. The new S8 packs a V8 motor but uses just 10.2 liters of fuel per 100km. Audi delivers that economy with its "Cylinder on Demand" technology. Before the S8’s launch this summer, we push Audi's luxury sportster to its limit.