The first time the Obama administration decided to hike fuel-economy standards for cars and light trucks, it wasn’t a terribly hard sell. This was back in May 2009, and the government had just bailed out GM and Chrysler, while California was threatening to move forward with its own plan for even more stringent fuel rules if the federal government couldn’t come up with a workable plan. Under the circumstances, the auto industry didn’t take long to agree to raise fleetwide CAFE standards to 35.5 miles per gallon by 2016. Easy enough.

 But now comes the hard part. The EPA and Department of Transportation are currently working on phase two of the CAFE plan, which would ratchet up fuel-economy standards anywhere from 3 percent to 6 percent per year between 2017 and 2025 — at its most ambitious, this new plan could mean a fleet-wide average of 62 miles per gallon by 2025. Is that even doable? If you ask advocacy groups like the Union of Concerned Scientists, cars and light trucks could probably get there with existing technology:

Conventional internal combustion engine vehicles can be made much more efficient by applying, for example, downsized turbocharged engines, six- and seven-speed transmissions, high-strength lightweight materials, enhanced aerodynamic designs, and more climate-friendly air conditioning systems. Some vehicles already on the road use a limited number of these technologies. However, all new vehicles could apply the full range of technology to maximize fuel efficiency.

 On the other hand, if you ask auto industry spokesmen, they sound a little more dubious. And, as Politico’s Darren Samuelsohn reports today, now that GM, Chrysler, and Ford are all profitable again, they plan to lobby a lot harder on the issue.

 

The big concern, for car makers, is that under the Clean Air Act, California is allowed to craft even stricter fuel-economy rules than the federal government — and, if it came to that, a dozen other states have said they’d join California. That means, should the new CAFE rules prove too weak, the states will strike out on their own — a hefty bit of leverage. That’s why Ford CEO Alan Mulally has been on the Hill this week, meeting with House Republicans, asking them to block California’s authority. (This Daily Tech report muses that some Republicans might find themselves in a “philosophical dilemma” over the issue because of their belief in states’ right, but does anyone really think they’ll have a hard time making an exception for California?)

The other thing that could affect the final rules is the ongoing bureaucratic tug-of-war between the Department of Transportation and the EPA. For a long time, the National Highway Traffic Safety Administration (NHTSA) was in charge of putting in place CAFE standards written by Congress. Then, in 2007, the Supreme Court ruled that the EPA had jurisdiction over greenhouse gases — including carbon-spewing cars — so now both agencies are in charge of the rules. Of the two agencies, NHTSA is considered more sympathetic to car makers, and, as Samuelsohn reports, NHTSA is trying to reassert control over the process, especially in getting its own cost estimates adopted.

In any case, the final numbers will matter a lot. If the new standards are on the lower end and the government increases fuel-efficiency by just 3 percent a year between 2017 and 2025, then, according to an EPA analysis, we’d end up saving about 700 million barrels of oil per year. On the higher end, we’d save about 1.3 billion barrels — which is roughly equivalent to all of our imports from Saudi Arabia, Libya, Nigeria, and Venezuela in 2009. So there’s a lot riding on these dry bureaucratic battles and haggling over arcane rules.

Brad Plumer is an associate editor at The New Republic