Ive noticed that all the small and very low emission engines have to be driven in a special way per engine type, most normal drivers don't give two hoots as to how they drive and it is in their mind only the car that can produce economical/low emission numbers and hence they often blame the car,
99% of the population just want to get in the car and drive it how they where taught to drive, they don't expect every new car that comes along will need new training on how to get the best out of it.
These are a mass produced car for the general public, they quote figures of economy claiming low emissions (high MPG) do the general public not have a right to expect their car will achieve near to the claimed figures without having to relearn how to drive??
The Prius V M5 analogy is just silly as the M5 was designed to be raced and was barely breaking a sweat, where as the prius was being ragged around at its limit.
Which gets better fuel economy a diesel locomotive pulling 1000 tons of freight train or a fiat panda, doing the same.....