Federal regulators said an annual improvement of 6 percent a year may be possible in the 2017-to-2025 time period in a report last year.

“We have a stated goal of not fighting change but embracing it, and achieving it as best we can,” Akerson told reporters today after meeting with U.S. lawmakers in Washington. “The laws of physics are not going to be suspended.”

GM is rebuilding trust with U.S. car buyers through better- built cars like the Chevrolet Cruze and the plug-in electric Chevy Volt, Akerson said last month. The company is looking to ramp up Volt sales to 45,000 next year as consumers take advantage of a $7,500 federal tax credit.

The need for continuing tax credits to spur sales of electric vehicles and more vehicle-charging stations in cities were also discussed at today’s meeting, Akerson said. The talks included new House Energy and Commerce Committee Chairman Fred Upton, a Michigan Republican, and U.S. Senators Carl Levin and Debbie Stabenow, both Michigan Democrats.

Lawmakers will be examining how the $7,500 federal electric-vehicle tax credits are distributed, Levin told reporters after the meeting. The credits run out for after 200,000 customers for each manufacturer claim them, and it may be possible to lift that limit, he said.

“There’s a complex formula that we’ll all take a look at,” Levin said. “Some companies aren’t using them. Maybe it can shift some.”

GM, which reorganized under Chapter 11 of the U.S. bankruptcy code in 2009, restructured its business before a $23.1 billion initial public offering in November, eliminating jobs, closing plants, renegotiating labor agreements and decreasing the number of dealers in its U.S. network.

The U.S. government owns about one-third of the company, down from a majority stake before the IPO.