The writer co-chairs the Bipartisan Policy Center’s Energy Project.

Even in our polarized polity, people from all sides of an issue can come together and do what’s good for the nation. That’s what happened with new mileage standards, to be finalized this summer, which will give drivers in our car-loving country an average of 54.5 miles per gallon by 2025. The standards were recently sent to the Office of Management and Budget for final review.

They build on gas-mileage boosts mandated during George W. Bush’s administration, addressing what Bush called our “addiction” to oil. When President Obama announced plans for further mileage improvements, auto executives stood with him in support. The 54.5 mpg standard has been endorsed by a wide slice of society, including national security leaders and consumer groups, business organizations and unions, and public health advocates and institutional investors.

Given this remarkable unity, I was dismayed that Mitt Romney told the Detroit News he’d look at undoing 54.5 mpg if he wins the White House.

This Republican says to Romney and the rest of the GOP leadership: Please don’t politicize a nonpartisan issue that the country has already resolved. The effort will probably backfire.

Giving Americans more miles per gallon is good for our economy, our national security, the environment and our pocketbook. Not incidentally, the new fuel-efficiency requirements — including an interim step of 35.5 mpg by 2016 — constitute the most significant federal policy yet toward reducing the heat-trapping gasses that are warming the planet.

Take a close look at the deal that auto executives struck when they embraced the new fuel-efficiency standards: It allows them to make uniform engines for the entire country, rather than different engines for use in California and the 13 states that have opted to follow its rules.

When I was Environmental Protection Agency administrator for President George H.W. Bush, the nation’s average gas mileage was around 25 mpg. For years afterward, U.S. drivers saw almost no advance in gas mileage, despite progress in every other field of technological endeavor: Phones went cellular, computers went from desks to laps and the Internet rose from curiosity to necessity. Meanwhile, the rest of the world developed technologies that offer safety and comfort along with excellent gas mileage.

George W. Bush finally got the ball rolling again, and Obama’s 54.5 mpg goal is the logical next step. It is ambitious, yet technologically doable. One auto executive tells me that his engineers are energized and excited by the challenge of meeting the new standard and confident they can do it.

Automakers know that this goal is also good for business; otherwise, they wouldn’t have signed on. They know that better gas mileage drives sales, especially in these times of high and volatile prices at the pump.

Last year, household gasoline expenditures set a record, averaging more than $2,850, and for most drivers, the cost of filling the tank over the life of a vehicle exceeds the cost of the car itself.

The Detroit News quotes Romney as implying that there’s a dichotomy between the cars people want and cars that get better gas mileage. It’s more correct to say that U.S. car buyers want both performance and fuel efficiency. The new standards grade vehicles on a curve so that SUVs don’t have to get the same mileage as compact cars, but all vehicles will have to be more fuel-efficient.

Poll after poll shows that Americans want vehicles that go farther on a gallon of gas. Kelley Blue Book’s latest consumer survey found that 66 percent of people in the market for a new car say gas mileage is a key factor in their decision of what to buy.

Improving fuel efficiency is also an essential part of reducing our nation’s dependence on foreign oil, since about two-thirds of imported oil goes to transportation. The 54.5 mpg standard would save us 2.2 million barrels of oil every day by 2025 — half of what we import from OPEC daily.

Burning less oil also means less pollution, which means a healthier population, lower medical costs and fewer workdays and school days lost.

It is difficult to see what advantage could be gained by abandoning a policy that is broadly supported and that will prove so beneficial.

Americans of all stripes can be proud that, when it comes to gas mileage, the government is working as it should, bringing all sides of an issue together and moving the nation forward.