Interesting developments:
Mercedes-Benz Bionic car: Boxfish stability and agility paradox finally solved.
Boxfish swimming paradox resolved: forces by the flow of water around the body promote manoeuvrability | Journal of The Royal Society Interface
So, the question become, how much of Mercedes' quoted fuel efficiency comes from the aggressive taper, kammback, clean lines, wheel skirts and drivetrain design of the car - and how much from the 'biomimetic' aspects of the design?