"funkyoldcortina" wrote in message
...

That's not true for the Prius. You still get better mpg than a
conventional petrol car on motorway trips, as once you're up to speed you
can ease off the pedal and the electric motor does most of the work to
keep you at-speed, requiring much lower power output from the engine.

Well that's plain rubbish.
If the electric motor is doing the work then it has to get its energy from
somewhere.
It can't be the battery or it would go flat.
If its from the alternator then its the engine that's driving that.
How can you get better efficiency by driving the alternator to make
electricity and then using that electricity to drive the motor rather than
using a fixed ratio gear?