U.S. regulators will release next week formal fuel-economy and tailpipe emissions rules for 2017-2025, according to a timetable set down two months ago.

Sources tell WardsAuto the final rule could come as early as Nov. 16, the eve of the Los Angeles Auto Show.

“It would be an unbelievably important day for the automobile industry and anyone concerned about the nation’s dependence on oil,” says David Friedman, deputy director-vehicles program at the Union of Concerned Scientists, a group advocating stricter standards for auto makers.

The rules, according to a preliminary release in July, call for auto makers to achieve a fleet-wide fuel-economy average of 54.5 mpg (4.3 L/100 km) by 2025. Such performance equates to carbon-dioxide emissions of 163 grams per mile.

The fuel-economy of passenger cars would jump 5% annually beginning in 2017, while the light-trucks requirement would increase 3.5% in each of the first five model years of the new rules, and by 5% in the final four model years.

The program also includes a mid-term evaluation, where the National Highway Traffic Safety Admin., the Environmental Protection Agency, and California regulators and auto makers will review its efficacy and the likelihood of hitting the 2025 target.

The looser standards for light trucks and the mid-term assessment were seen as key wins for the auto industry.

“I wouldn’t expect any big changes,” Friedman tells WardsAuto. “In fact, I would be surprised and disappointed if there were.”

However, the 2025 plan lacked important details so the proposed rule’s originally planned September release was postponed to this month.

Auto makers still sought direction on what sort of credits they might receive for producing and selling zero-emissions vehicles, such as the Nissan Leaf electric vehicle.

Environmentalists, meanwhile, sought a clearer definition in the rules between passenger car and light truck, hoping to block auto makers from potentially trying to classify additional vehicles as light trucks to more easily achieve the mandate.

California, which abandoned its usual lone-wolf approach to regulation by adopting the federal mandate, wants the 2025 regulations to bolster its efforts to accelerate the rollout millions of hybrid, plug-in hybrid and fully electric vehicles.

The 2025 rules are expected to become law next summer.

Auto makers currently are stepping towards fleet-wide performance targets of 35.5 mpg (6.6 L/100 km) and 250 gpm CO2 by 2016.

Negotiated over a 2-year span, the 2025 and 2016 programs represent the nation’s boldest action to improve fuel economy and reduce tailpipe emissions in more than 35 years.

Auto makers historically have resisted stricter fuel-economy and emissions regulations, saying the rules put them at odds with consumers who traditionally are not highly motivated by efficiency.

But auto makers have softened their stance in the wake of 2009’s taxpayer-funded bailout of bankrupt General Motors and Chrysler, as well as the millions of government dollars made available through loans and grants to design, develop and build more efficient vehicles.

jamend@wardsauto.com