I have recently bought a new Vauxhall Astra 1.5 turbo Diesel Automatic. The car has the facility to change speed according to road signs. and limits the speed to 20mph regardless of how far you press the accelerator.
Now the manufacturer advises it can achieve 54mpg combined urban/Highway, however in the numerous 20mph zones in Edinburgh it is achieving 37.3mpg, significantly less than the tests suggest. Do electric vehicles suffer the same real world dramatic drop that the Kinetic theory suggests does not exist. The car while in 3rd gear is at 1300rpm. So I would tend to disagree with this 19th century equation. I am looking at an electric vehicle, for urban use(utterly useless in real world motorway driving).