I've always wondered why there hasn't been a vehicle with individual electric motors on each driving wheel and a separate highly tuned " stationary " engine to generate the electricity for the driving motors . Less moving parts - less loss of energy through friction & other inefficiencies. Much greater fuel efficiency from a motor designed to operate only at the "sweet spot" rather through a wide range of revs. The engine could generate electricity that is stored in the short term by a small "battery" more like a capacitor to smooth out the ups & downs of the load from the electric motors ??

