That is one year later than the target set under the Obama administration, which said that requiring vehicles to be more fuel-efficient would improve public health, combat climate change, and save consumers money at the gas pump without compromising safety.
The compromise between the California Air Resources Board and Ford, Honda, Volkswagen, and BMW of North America came after weeks of secret negotiations and could shape future USA vehicle production, even as White House officials aim to relax gas mileage standards for the nation's cars, pickup trucks, and SUVs.
A joint statement from the four automakers pointed to the need for regulatory certainty in striking the deal with California.
The Obama-era rules adopted in 2012 called for a fleetwide fuel efficiency average of 46.7 miles per gallon by 2025, with average annual increases of about 5 percent, compared with 37 mpg by 2026 under the Trump administration's preferred option.
Under the deal, automakers will have to increase the average fuel economy of their new vehicle fleets to almost 50 miles per gallon by model year 2026, which is an increase of 3.7 miles per gallon per year, and would ultimately make new cars much cleaner.
"What we have here is a statement of principles meant to reach out to the federal government to move them off the track that they seem to be on and onto a more constructive track", Nichols said, adding that the companies approached California officials last month about a potential compromise. "This agreement represents a feasible and acceptable path to accomplishing the goals of California and the automobile industry", she said. The deal roughly matches the cleaner vehicle plan put in place by the Obama-era Environmental Protection Agency - a plan that the Trump administration has been working feverishly to undo since the president took office in 2017.
Both the administration and the automakers' lobbying groups have argued since the start of the rollback that, by setting higher standards than the federal government, California could bifurcate the United States market.
"The federal government, not a single state, should set this standard, " said White House spokesman Judd Deere in an e-mail.
Officials from the National Highway Traffic Safety Administration, which is co-writing federal tailpipe standards, issued a statement saying the administration's proposal does not prevent manufacturers from building more-efficient vehicles if they so choose.
Becker also says the emissions standards put in place under the Obama administration, which are slightly more restrictive than the California agreement, should be maintained.
Other US market share leaders like Daimler and Nissan did not immediately respond to a request for comment. One percent of that annual improvement could be covered by credits awarded for building electric vehicles.
On June 6, 17 major automakers wrote a letter to President Donald Trump and California Governor Gavin Newsom seeking to revive talks and urging a compromise "midway" between both sides to avoid "an extended period of litigation and instability". The White House rejected that effort and automakers and California launched private talks.
Automakers credit Trump with reopening the requirements after the Obama administration in its final weeks had sought to lock in the requirements through 2025.
"The Trump administration is hell bent on rolling [emissions standards] back". Under federal law, the state of California is allowed to promote more stringent vehicle emissions standards. "I now call on the rest of the auto industry to join us, and for the Trump administration to abandon its regressive proposal and do what is right for our economy, our people, and our planet".