The upcoming CAFE standards are making carmakers nervous, with most of the major players speaking out about the huge cost and difficult technical challenges they face. High-tech plug-in hybrids like GM's Volt and Toyota's recently confirmed car have been the central hope for getting fleet averages down before the 2015 deadline, but GM isn't so sure thinks will work out in time.

Unfortunately, the same technology that makes them efficient makes them expensive and difficult to built in large numbers, and for that reason, GM has told the government not to count on the Volt for huge fuel savings in the near term, reports the Detroit Free Press. The Volt's first full year of production will be 2011, with only a few months of 2010 seeing full-scale Volt output. By 2011 GM hopes to be rolling 10,000 of the plug-in hybrids from their factories, ramping that number up to 60,000 annually by 2012.

It's easy to see why GM is telling the government the Volt won't have a huge impact on fleet numbers - even under best-case circumstances, fewer than 500,000 Volts will be sold before the 2015 deadline, a tiny fraction of the company's overall sales through the next 7 years. With such a steep ramp-up cycle and with materials prices rising and driving up the projected cost of the car, the Volt is not likely to reach best-case scenario figures.

That sentiment is backed up by the words of GM's briefing on the so-called EREV, or extended range electric vehicle, technology to the NHTSA as it attempts to build models of the coming fuel economy regulations. “We strongly discourage NHTSA from applying either PHEV or EREV technology in any significant volume in its … model during the 2011-2015 timeframe," the company said.