use the FCC to increase CAFE standards?

With the buzz about the auto industry still fresh in our minds and $4/gallon gas not far behind us*, I thought it wuld make sense to unleash this idea on the world through the vehicle of my undervisited blog. If we're serious about raising CAFE (average fuel economy) standards, why don't we mandate that a certain percentage of the screen be occupied by white numbers that represent the MPG of any given vehicle being advertised and the CAFE of the manufacturer running the ad? It seems to me that this would be simple and effective in both increasing awareness about what kind of fuel economy any given vehicle delivers as well as incenting companies to improve their fleet performance without harming any of them unnecessarily. 

*I never miss an opportunity to point out that Lester Brown, whose book Plan B 3.0 is freely available for download, makes a compelling case that the true cost of a gallon of gasoline is about $8 / gallon.