Great Mileage won't kill the Oil companies... It will just make people drive more and leave the lights on more...
That is the history of things like that... You go from a car getting 10 MPG's to a care getting 30 MPG's >>> You find yourself driving 3 times further than you did before.

Here is something to think about... You live as much as you can afford & You drive as fast as you can afford.

Oilguy