The federal Environmental Protection Agency said on Thursday that manufacturers would no longer earn a credit for installing engines that automatically turn off when vehicles come to a complete stop and restart when drivers take their feet off the brake pedal.
The start-stop feature is meant to save fuel and reduce emissions, but the Trump administration rejected the scientific finding that the government used to support vehicle emission reduction regulations, making it possible to eliminate the credit.
Until Thursday, carmakers could be fined if their vehicles with a model year of 2012 or later did not meet a greenhouse gas emission standard, and these credits could be used to help reach that limit.
The E.P.A. administrator, Lee Zeldin, said in a news release that start-stop kills vehicle batteries. However, that is a common misconception, according to experts, including Consumer Reports.
“As I traveled across all 50 states this past year, I heard from countless Americans who not only dislike the start-stop feature but passionately advocated for this mechanism to be a thing of the past,” Mr. Zeldin said.
He said in May 2025 that the administration was working to get rid of the credit, which he said “everyone hates.”
The number of vehicles with start-stop steeply increased starting in 2012, when the E.P.A. made it so car companies could earn a credit toward federal emissions rules by installing the feature in vehicles.
It was not a popular new technology.
In 2022, more than 1 percent of all automobile defect complaints collected in a Transportation Department database were related to start-stop. Vehicles with a 2017 model year were most likely to have reported problems.
The percentage of complaints fell almost by half by 2024, even though the feature had been added to even more vehicles.
Some vehicle owners don’t like the feature because they don’t believe that it saves gas. Others are concerned it wears down the engine.
Most vehicles have a feature so the driver can turn start-stop off during a trip, but a feature to disable it completely would have blocked companies from getting the credit.
Research shows that start-stop reduces fuel use and cuts emissions. Depending on driving conditions, stop-start improved fuel economy between 7.27 and 26.4 percent during testing, according to a 2023 technical paper by SAE International, an organization formerly known as the Society of Automotive Engineers.
The program has undergone many changes in stringency through the years, and it’s possible the next administration changes course. Vehicle manufacturers may continue to install start-stop, even though the credit is not available.
John Bozzella, the president and chief executive of the Alliance for Automotive Innovation, which represents car companies including Honda, Ford and General Motors, said in a statement provided to Car and Driver that the policy change corrected “some of the unachievable emissions regulations enacted under the previous administration.”
The start-stop change is part of a move by the Trump administration to roll back regulations to improve fuel efficiency in the United States, where transportation is the largest source of greenhouse gases.
The start-stop credit is part of the “off-cycle” credits program, which rewards vehicle manufacturers for using technologies that provide real-world emission-reducing benefits but have not demonstrated those benefits entirely during vehicle testing.
The administration on Thursday eliminated all “off-cycle” credits, which also include technologies like reusing engine heat to heat the car’s interior and reflective paint to keep cars cool.
Also Thursday, the Trump administration rejected the scientific finding that climate change endangers human health and the environment, which the government has used for nearly 17 years to justify limits on carbon dioxide, methane and four other greenhouse gases.
The scientific determination, known as the endangerment finding, was based on more than 200 pages of research and evidence. Mr. Trump on Thursday said the finding “had no basis in fact.”
Ben Blatt contributed reporting.
Amanda Holpuch covers breaking news and other topics.
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