It seems that it will go the way of the dodo.
I do not mean American car companies, but cars that one would think of as American: big, muscular and running on gas. Instead, with the announcement that the Obama administration made about increasing and accelerating the gas mileage requirements to 39 mpg by 2016 (not to mention that government pretty much owns GM and Chrysler), it would mean that we would be more European in our car choices: For the masses, if they can afford a car, it will be smaller, lighter, more expensive and running on diesel or hybrid. For the elites, well they will have more choices as they will have the money to pay for the fees that the luxury car companies charge to pay the federal government in penalties for not meeting the mileage requirements.
Can’t say that I am happy about this….
Yeah, it’s a bit too high a lot too fast!
39 mpg is not an easy number to achieve! That means no more V8’s and a lot of (if not most) V6 engines! 
Oh well…
v6? Shoot, it will be 4 cylinders or less.
A gallon of gas only has so much energy and even with converting some of the lost heat energy to recharge batteries for hybrid motors, I am guess we are about as efficient as we can get for gasoline engines (unless someone invents frictionless motors) – so that leaves us with chopping weight off which studies have shown causes more fatalities.
I guess like frictionless motors, someone can create some magic material that is light and strong but think of the cost of the car and not to mention that the fabrication and engineering of such things would probably be using hazardous and rare materials and take huge amounts of energy.