The Environmental Protection Agency is set to reverse Obama-era regulations on vehicle fuel economy standards.

Under the Obama administration, the rules would have required automakers to increase the average fuel economy to 54.5 miles per gallon by 2025 and reduce greenhouse gas emissions.

“If fully implemented, the rules would have cut oil consumption by about 12 billion barrels over the lifetime of all the cars affected by the regulations and reduced carbon dioxide pollution by about six billion tons,” stated Hiroko Tabuchi for the New York Times.

Manufacturing fuel-efficient cars can be expensive for automakers. In anticipation of this, the Obama Administration proposed a system in which automakers could earn credits for over compliance to the standards, according to a report by the research organization Resources by for the Future (RFF).

For example, vehicles that exceeded the miles per gallon standard set by these rules would earn credits.

These credits would allow manufacturers to, “use credits from over compliance in one fleet (e.g., cars) to achieve compliance in the other fleet (e.g., trucks),” and “[…] bank credits from over compliance in one year to use for compliance in a future model year,” according to RFF.

But now the E.P.A. plans to loosen these regulations.

Automakers have long been opposed to the fuel economy standards set by Obama. They stated that creating vehicles to meet these standards would be too costly, and said in a letter to Pruitt that they would have to spend “$200 billion between 2012 and 2025 to comply with the rules,” according to the New York Times.

And those in favor of lowering fuel economy standards said that it will provide incentives for automakers to add more jobs in their American factories, invest more in vehicle-safety technology, and lower the cost of vehicles.

E.P.A. Administrator Scott Pruitt also announced that the agency will challenge California’s authority to implement stricter clean air standards.

Under the Clean Air Act, California was granted a waiver giving it the authority to regulate its own tailpipe emissions. The state, along with twelve others, is suing the E.P.A. for violating the Clean Air Act and unlawfully weakening auto emissions rules, according to the New York Times.

By choosing to adhere to the Obama-era regulations, the auto market would be split into two sectors as manufacturers would have to make cars that matched higher fuel efficiency standards for one, and not for the other.

Many automakers are willing to compromise with California to avoid this. “We want one set of standards nationally,” said Ford Motor Company’s top leaders in a blog post. They also said they opposed a rollback of the Obama-era regulations.