Washington Is Rewriting the MPG Rules, and the EV Math Changes With Them

Fuel economy rules do not sell a single electric car. They do decide how expensive it is for an automaker to not sell one, which is why the rewrite now working its way out of the US Department of Transportation matters more to EV product planning than most of the launch events on this year's calendar.

Transportation Secretary Sean Duffy said on Monday that new corporate average fuel economy standards will be announced shortly. The final text is not out, but automakers expect it to track closely to the proposal NHTSA issued in December 2025: a fleetwide average of 34.5 mpg by 2031, against 50.4 mpg under the Biden-era rules.

Duffy framed it in Michigan in the plainest possible terms. "We are about to announce a common-sense fuel economy standard because we want Detroit to build cars that Americans want to buy — not cars that Democrats want Washington to build," he said.

Sixteen miles per gallon of fleet average is an enormous amount of regulatory slack. The Biden schedule it replaces demanded 8 percent annual efficiency gains for the 2024 and 2025 model years, 10 percent for 2026, then 2 percent a year through 2031 — a ramp that only really closed if manufacturers kept adding electrified models to the US mix. Take the ramp away and the business case for each of those models has to stand on its own.

NHTSA's own arithmetic on its December proposal, as reported by GM Authority, is unusually candid about the trade. Roughly $930 off the average new vehicle price. About 100 billion additional gallons of fuel burned through 2050, $185 billion more spent on it, and carbon dioxide emissions up around 5 percent.

Buried in the draft is a change with more product-planning consequence than the headline figure. CAFE has always treated light trucks more gently than passenger cars, a distinction dating to 1975, when pickups and SUVs were largely commercial tools. They are now commuter vehicles, and NHTSA appears ready to say so.

Autoline Daily, citing Detroit News reporting on the draft, describes NHTSA proposing that genuine work trucks average 28.6 mpg by 2031 while cars and passenger trucks are held to 37.4 mpg. Detroit News gives the same pair of figures for the draft's 2031 requirements. If a three-row SUV or a crew-cab pickup gets counted against the car target rather than the truck target, a regulatory rollback stops being a rollback for the companies whose volume lives in exactly those segments.

That is why, per Autoline, lobbying has already started to have all trucks counted as trucks. The rollback and the reclassification pull in opposite directions, and until the final rule lands nobody knows which one dominates.

A separate move went through last week with far less noise. NHTSA issued a final interpretive rule narrowing the scope of fuel efficiency standards for medium- and heavy-duty trucks, as the Washington Examiner reported. The agency's position is that the existing standards reached beyond what the statute allows and "restricted manufacturers' ability to design innovative approaches to meet commercial truck fuel efficiency standards," and that its authority extends to vehicle fuel efficiency but not to standalone engines or individual components.

The rule repeals nothing on its own. It builds the legal footing for a future rulemaking that would. For anyone selling electric trucks and depot charging into US fleets, that is a slow-burning problem: the diesel comparison those products are measured against gets a longer runway, at a moment when diesel prices are near record highs and the operating-cost argument was doing the heavy lifting anyway.

Strip out the supports one at a time and the picture gets stark. Congress removed federal penalties for missing fuel economy targets in 2025, which made CAFE compliance a paperwork exercise rather than a financial one. It ended the $7,500 consumer tax credit. It rescinded California's authority to bar new petrol vehicle sales from 2035, a decision the state is contesting. Now the underlying targets themselves are being cut, and the credits automakers banked in earlier years become more valuable still under a proposed retroactive adjustment to the 2022 standard.

What survives is unglamorous and durable: cost per mile, the fact that an EV is nicer to drive than the thing it replaced, and the parts of the world that are not the United States. Chinese and European targets have not moved. Neither have the battery cost curves. A US manufacturer that reads the new rules as permission to slow down is making a bet about the next five years, not the next fifteen, and it will be competing globally against firms that were never given the option.

The nearest analogy is not deregulation so much as a deadline extension on a project nobody wanted to start. The work still has to happen. It now happens on the manufacturers' timetable rather than Washington's, and the ones that were already committed keep their lead by default.