As for California's waiver, which was granted in 2013, the proposal says that the EPA will exercise its right to revoke that waiver since it finds the state's standards to be "arbitrary and capricious", unnecessary and inconsistent with parts of the Clean Air Act. But Trump's EPA said the efficiency rules drive up vehicle prices, keeping many people in older, less safe cars and trucks. California and other states are already suing the EPA.
The administration's proposal asserts that "attempting to solve climate change, even in part" is "fundamentally different" from the Clean Air Act's "original objective of addressing smog-related air quality problems".
Chet France, an EPA senior executive until his retirement in 2012, called the administration's contention that the mileage freeze would cause only a tiny increase in climate-changing exhaust emissions "bogus".
"There are compelling reasons for a new rulemaking on fuel economy standards for 2021-2026", said Transportation Secretary Elaine L. Chao.
The Trump administration has moved to weaken USA vehicle emissions standards and has set up a major confrontation with California by scrapping its ability to enact stricter pollution standards and mandate the sale of electric cars.
The proposal would freeze US mileage standards at levels mandated by the Obama administration for 2020, when the new vehicle fleet will be required to hit an average of 30 miles per gallon in real-world driving.
A lower emission standard would make it easier for them to make the vehicles more drivers want.More news: Honor 10 GT gets new Lily of the Valley color variant
The states that have adopted California's emission rules together make up about one third of the USA auto market. "We have been steadily increasing the standards... for nearly a decade", said EPA Assistant Administrator Bill Wehrum on a call with reporters Thursday.
Ultimately, the two agencies published Thursday's proposal jointly, and acting EPA Administrator Andrew Wheeler publicly defended the proposal during testimony Wednesday before the Senate Environment and Public Works Committee.
The Obama-era rules also drove auto prices higher, since prior estimates fell short of what incremental improvements to fuel efficiency actually cost.
The Trump administration proposal could also invalidate California's mandate that automakers sell a certain number of electric vehicles. They're trying to defend clean air standards that require automakers to build cars and trucks with an average of about 54 miles per gallon by 2025. A dozen other states and Washington DC also follow higher standards.
President Donald Trump listens as Rep. Marsha Blackburn, R-Tenn., speaks at a rally in Nashville, Tenn. on May 29, 2018. Consumers Union, the advocacy division of Consumer Reports, said consumers could save between $3,200 per auto and $4,800 per truck over the life of the vehicle under that standard, and that they would save even more if gas prices go up.
Trump's decision to challenge California's authority to regulate vehicle emissions upends decades of federal policy that allowed the most populous and richest US state to combat air pollution that particularly afflicts Los Angeles.
A drawn-out legal battle over the standards could hurt the auto industry as it tries to plan for coming model years.