Here's a piece in NRO, noting that, in time for Earth Day, the 2010 Mustang, motoring down the road at 70 mph, emits only 1.3% of the HC of a 1970 model.
But wait, there's more!
For purposes of this comparison, the 1970 Mustang in question was not making 70 mph. In fact, it is tested parked, as in a driveway, with the engine shut off.
The 2010 Mustang has reportedly met another milestone: It can produce 300 hp, and get 31 mpg, though probably not at the same time.
All you Greenies out there now have my express permission and encouragement to go suck an egg.