Let met get this straight... The government wants to mandate (or up the mandate) technology with new CAFE standards. And then the government wants to actually build the cars that meet the standards. Is the next thing on the agenda a mandate as to which car I should buy?
I'm just saying: this doesn't sound like it would go well. Presumably GM was already making their best guess at what was "most sellable" vs "most efficient". I say presumably because -- well, they haven't quite been successful lately. So mandating what will be sold via CAFE ... I'm not entirely sure that is going to go in GM's favor. The most recent numbers I could find online (or the most recent I found when I stopped trying) show the Honda/Toyota crowd to be well ahead of GM... almost to the point of meeting the new proposed standards. My guess is that a chip tweak and they are there (at the slight expense of horsepower).
Let the government test it at full efficiency... Then let the consumer choose.
The whole thing reminds me of A Nice Morning Drive -- which was a fictionalized product of the same type of government mandates as it was applied to safety. And if you don't recognize Morning Drive... shame on you.