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How Federal Fuel-Efficiency Rules Help Fight Climate Change

Research suggests passenger-car standards work well to lower countries’ emissions.

By Francie Diep


A motorist fills his car at a gas station near an oil field on February 12th, 2016, in Oklahoma City, Oklahoma. (Photo: Pat Carter/Getty Images)

In a visit to Detroit yesterday, President Donald Trump promised automakers that he would review the Obama administration’s fuel-economy rules for new cars. The review is widely considered a first step toward easing the requirement, set in 2012, that new cars and trucks must get an average of 54.5 miles per gallon by model year 2025.

The industry has long lobbied for a change in the rules, and Trump thinks it will help grow car-factory jobs. “The assault on the American auto industry is over,” he said in a speech to union workers.

Federal standards seem to push carmakers in a way that consumer demand for better mileage alone doesn’t.

President Barack Obama wrote the 54.5 mpg standard in hopes that it would help America fight climate change. But just how well do fuel-economy laws cut emissions? In other words, if American manufacturers return to a lower standard, how much will it hurt the environment, compared to keeping the current rule?

In 2012, the Environmental Protection Agency estimated Obama’s newest fuel-economy rule would save six billion tons of greenhouse gases from reaching the atmosphere by 2025. One team of economists argues it’ll be more like five billion tons. Either way, that’s a lot — more than a year’s worth of emissions for the country. Still, we don’t know yet how low Trump will aim, so we can’t say how much of these savings a new rule would undercut.

Why do fuel economy rules make such a difference? The rules affect a sizable contributor to America’s greenhouse gas emissions: In 2014, cars, SUVs, pick-up trucks, and minivans were responsible for 20 percent of the carbon dioxide the United States put into the air, according to the EPA.

Plus, these standards seem to push carmakers in a way that consumer demand for better mileage alone doesn’t. One working paper found that the European Union’s emissions standards encouraged automakers to develop new technology and to sell more efficient cars. In the U.S., after plateauing for decades, cars’ and trucks’ average fuel efficiency began rising in 2007, when Congress passed the first significantly stricter standard since the Energy Policy and Conservation Act of 1975.