Congress should pass a "consumer protection disclosure and warning label" law that requires the following:

1. The EPA fuel economy must be prominently displayed on all print and television vehicle advertising in a clearly legible type face that is at least the same size as the name of the vehicle or manufacturer, whichever is larger. For radio ads, the EPA fuel economy must be mentioned at the beginning and end of the spot. (Have you ever noticed how most car ads don't mention it at all?)

2. The EPA fuel economy must be permanently etched onto the bumper of all vehicles sold in the U.S. using a clearly legible type face that is at least the same size as the name of the manufacturer's make and model badge.

Then let peer pressure work its magic.