[pflanze]

> A 20 MPG car is not twice as efficient as a 10 MPG car.

Why not?

The page you linked doesn't talk about "twice as efficient", it talks about an absolute number of gallons saved per distance travelled.

Also, assuming there was no typo, vegardx's point was that "kWh/h per 100km" is invalid. "kWh/h" is the same as "kW", and "kW per 100km" (power per distance) is not describing vehicle efficiency, it's non-sensible. "kWh per 100km" (energy per distance) is.