TWO MONTHS ago, California offered what one senior state official described as an “olive branch” to the Trump administration. In the fight over how strict government fuel-efficiency standards should be, the state struck a deal with several automakers that would give them more flexibility and time to make their fleets use less fuel and propose lower emissions. This should have prompted the Trump administration, which has been seeking to loosen the standards, to negotiate a deal with the state and carmakers on uniform national efficiency norms. Instead, the Trump Environmental Protection Agency and Transportation Department are expected to slap away California’s olive branch at a Thursday news conference. Hardly anyone would gain from such a pigheaded move.

The fight stems from a quirk in the Clean Air Act that allows California to set its own auto-efficiency rules under a federal waiver. Other states can then adopt California’s rules as their own. Many have done so, and this bloc of states adds up to more than a third of the U.S. auto market. Yet the Trump administration wants far weaker rules, and it does not want California to spoil its deregulatory effort. For their part, carmakers are terrified that they will face strong efficiency standards in some states and not others; they want the clarity of a single, national program. But instead of forging a deal with California, the Trump administration has reportedly decided it will try to revoke California’s waiver to regulate on its own, an unprecedented move that the state will challenge in court.

The state has a good legal case, but the battle could take years, and the fact that the question of whether a state’s waiver can be revoked has never been tested adds some uncertainty to the outcome. The bigger point is that all this time, effort and rancor are unnecessary: Why wage such a battle simply to increase fuel waste and pollution?

The administration has offered various rationales for its insistence on rolling back standards that the Obama administration and California had previously established, which would have increased average car and light truck fuel efficiency to 51.4 miles per gallon by 2025. For example: Though consumers would save money over time on gasoline purchases, higher initial sticker prices might deter them from buying newer and better cars, which could leave more old clunkers on the road.

These arguments are not wrong so much as they miss the point. Auto-efficiency standards might not be the best strategy for cutting emissions and fuel waste from the transportation sector — a higher gas tax or a carbon tax would be better. But, at the moment, efficiency rules are the legal way to do so. And the ones the Obama administration and California established would undoubtedly help: The experts at the Rhodium Group determined last year that the Trump administration’s push to wipe away auto-efficiency standards would result in the national fleet reaching only 38 mpg. The result would be higher oil consumption on the order of 221,000 to 644,000 barrels of oil per day by 2030 — and 28 million to 83 million metric tons more carbon dioxide in the atmosphere. Drivers would not really benefit, because they would end up paying billions more in gasoline costs.

The Trump administration should abandon its destructive course and compromise.

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