Automakers are asking the Trump administration and California to restart negotiations over future fuel economy standards, worried about disruption in their business model if the two sides can't come up with a new, single national standard.
The problem facing automakers is partly of their own making. Car companies in the U.S. asked a newly elected President Donald Trump to relax the Obama administration's finalized fuel economy standards for 2020 through 2025.
A New York Times investigation published in December found that other groups rushed through the door that the automobile lobby opened.
Marathon Petroleum, billionaire industrialist Charles G. Koch and oil industry lobbyists, among other groups, engaged in a stealth campaign to urge the federal government to roll back the standards, or even abandon fuel economy standards altogether.
To the dismay of automakers, the EPA chose to freeze the standards after 2020, rather than modifying them.
To implement the rollback, the government will have to revoke California's EPA waiver that allows the state to set its own standards. California says it will sue if that happens.
Such a lawsuit could take a long time to make its way through the courts, thus derailing the regulatory certainty that automakers need to develop future products, many of which take three years or more to make it from the drawing board to dealer showrooms.
In the meantime, if the courts do not agree to let the EPA suspend California's waiver during the expected legal proceedings, automakers may need to keep making vehicles that meet California's standards.
More than a dozen states have chosen to align their standards with California's, which the EPA waiver allows them to do.
Otherwise, for awhile, automakers might have to develop and build two different versions of each vehicle: one that can be sold in California and states that follow California, and one that can be sold in the rest of the country.