This of course hints at the major problem with car efficiency, which is excess weight. Federal safety mandates have made cars way more heavy than they used to be, so that despite 20% improvements in engine efficiency modern gasoline cars merely match the cars of 30 years yore. The big culprit, from what I gather, is the roll safety requirement. Take a hacksaw and welder to a modern sedan and electric doesn't really make much sense. Gasoline is still the way to go.