“Different stakeholders have different views,” the official said.

China uses a different system from the United States to regulate fuel economy. China sets minimum standards for each of 16 weight categories and tests only urban fuel economy, not highway driving.

Image With hazy smog a frequent condition in Beijing and other Chinese cities, China is seeking ways to impose more fuel efficiency. Credit... Frederic J. Brown/Agence France-Presse — Getty Images

Adjusting for these differences is difficult and controversial. Mr. An estimated that the average new car, minivan or sport utility vehicle in China already gets the equivalent of 35.8 miles a gallon this year based on the American measurement system of corporate averages and will be required to get 42.2 miles a gallon in 2015.

By comparison, President Obama announced last week that each automaker will be required to reach a corporate average of 35.5 miles per gallon by 2016.

The details of China’s new fuel economy standards may favor domestic automakers at the expense of multinationals, several auto industry officials said. That is because the new rules call for the steepest increases in fuel economy  as much as 26 percent  for midsize and compact cars, market segments where multinationals are strong. Subcompacts, a market where domestic automakers are stronger, will be required to increase their gas mileage by as little as 9 percent compared with the existing standards, which took effect on Jan. 1.

Large cars, minivans and sport utility vehicles will face percentage increases between those extremes. The Chinese government had already cracked down on these vehicles by setting very high gas mileage benchmarks for them as part of the existing rules.

When told late Wednesday of China’s gas mileage plans, Michael Dunne, the managing director for China at J. D. Power & Associates, the consulting firm, said that Japanese, Korean and German automakers had models of very small cars that they might start building in China if they have trouble meeting the new standards for larger models.

“The short-term impact is it would favor the Chinese, no doubt about it,” he said. “Global automakers care so deeply about this market that they’ll do whatever it takes, and adjust.”