for me, 150 mpg and above. (that’s not a typo)
but I would be willing to go down to 50 to 70, depending on size.

“1. The New Standards

* The Obama Plan will be a single new national standard for all cars and light trucks. [NY Times]

* The standard will be almost 40% cleaner/ more fuel-efficient by 2016 than it is today.

* Cars will be required to get an average 35.5 miles per gallon (similar to the goal of the California plan); the current standard is 25 miles per gallon.”

Source

Volkswagen seems to have a fuel efficient car. Here is an article about a concept car of theirs that supposedly gets 240 miles to the gallon.

@Bluefreedom
here
is the new version. they made it a bit less aerodynamic, more powerful and probably heavier too.
Does 160mpg now.

http://www.youtube.com/watch?v=kasCn1K7Reg

Posted an hour ago: http://www.fluther.com/disc/56705/what-is-considered-a-fuel-efficient-car/