I think the keyword here is SIGNIFICANTLY. Sure we'll see some people switch back to a large sedan & go from 16 in the city to 24-26. But IMHO that's simply not enough since the way people continue to drive they'll be getting 22MPG.

People here in the US simply aren't ready to accept sub 2 liter engines & the concept of a commuter car.

"Speed doesn't have anything to do with mileage. My truck has an overdrive gear for a reason." - Credited to an unnamed Freeper reguarding changing the speed limit back to 55MPH.