err... skyactiv is not a hybrid, and i think bigger capacity engine will be in advantage as the engine keeps running during idle, or not all energy efficiently converted to mileage. some v8 engine stops 4 of the cylinders when less power needed, hybrid can stop the engine during idle, range extender runs the engine only when battery runs low. mercedes has the s400h, i think a 3.5 v6 hybrid powertrain... mazda 6 is not expansive enough compare to prius (after tax)