My thoughts on MPG Equivalent -
Don't bother calculating in efficiency of a coal plant OR how much energy it takes to find and dig oil wells.
If you really want to do a true "wells-to-wheels", it gets VERY complicated (and political) very fast.
Measure power from the wall and gas from the pump. It's the only fair way to do it.
An electric car being about 4 times as efficient? That sounds about right.
And remember, with an electric car, you can get your electricity from solar panels, wind power, nuclear plants, coal plants, hydro, etc., etc. - it's your choice - you get to choose where your power comes from.
You can't do THAT with gasoline.