What the new electric-vehicle mileage rule actually changes.

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I. The bottom line

The Department of Transportation’s new corporate average fuel economy (CAFE) rule, finalised on May 1, raises the fleet-wide mileage target for new vehicles to 49 mpg by model year 2032. The current standard, set in 2022, is 41.6 mpg by 2026. The new rule is a 17.7% increase from there.

The rule does three things that aren’t obvious from the press release. First, it doubles the per-vehicle credit automakers earn for selling EVs — making it easier to hit the fleet target without changing internal-combustion economy. Second, it carves out a new exception for vehicles weighing more than 8,500 lbs, which has the practical effect of giving full-size pickups a freer pass than the previous draft did. Third, it lets manufacturers carry forward unused credits from 2024 + 2025 into the new framework.

II. What changed in the final draft

The proposed rule, released in February, set the 2032 target at 52.6 mpg. The final rule is 49 mpg. Two automakers I spoke with said the change came from a single line of comments by the Office of Management and Budget questioning whether the higher number was achievable without forcing a fleet shift to small cars that consumers don’t want. The DOT denies that’s why the target moved. The OMB declined to comment.

The 8,500 lb exemption is more consequential than its small footprint suggests. Fewer than 8% of vehicles sold last year crossed that weight threshold, but those vehicles account for about 22% of fleet-wide carbon emissions because of how heavily they’re driven and how poor their economy is. By exempting them, the rule effectively narrows the regulated fleet by roughly a quarter of total emissions.

III. Why it nearly died three times

From conversations with three current and two former DOT officials over the past year:

February 2024: The first complete draft set the target at 56 mpg. Detroit lobbying delegations told the EPA + DOT that target was “structurally impossible” without a shift to small cars Americans wouldn’t buy. The number came down to 54 mpg.

August 2024: The Inflation Reduction Act’s EV tax-credit changes — specifically the sourcing requirements that disqualified most vehicles built outside North America — reduced projected EV adoption by 14% in DOT’s internal model. Without enough EVs in the fleet, the math didn’t work. The target dropped to 51 mpg.

March 2025: A late-stage OMB review challenged the cost-benefit analysis. The DOT was asked to either lower the target or substantially increase the projected co-benefit estimate. They lowered the target to 49 mpg.

IV. What to watch

Three things to watch over the next 18 months. First, the inevitable lawsuits. The American Petroleum Institute and the National Association of Manufacturers have both signalled they’ll challenge the rule’s methodology. The legal threshold is whether DOT can show its cost-benefit analysis is “not arbitrary or capricious”, which is a low bar. The most likely venue is the DC Circuit; the most likely judge is unfortunately the one whose ruling on the 2023 emissions rule was vacated by the Supreme Court last year.

Second, what California does. California has its own waiver to set stricter standards; that waiver was reaffirmed by EPA in March. California is already considering a 56 mpg target by 2032. If they go forward, eleven other states will follow, covering ~32% of the US new-vehicle market. Carmakers would be operating under two regimes simultaneously.

Third, the EV tax-credit fix. Treasury announced in April that they’ll relax the IRA sourcing requirements starting in 2026 model year. If that happens, the projected EV adoption rate that underpins the 49 mpg target becomes more achievable; if it doesn’t, automakers will struggle to hit the number even with the looser rule.

V. The honest version

The 49 mpg target is meaningfully more ambitious than the previous standard, but less ambitious than what the climate-policy community pushed for and less ambitious than the original draft. The exemptions and credit-carryforward provisions take more bite out of the rule than the headline number suggests. It’s a real piece of policy — not the strongest version anyone could have written, not the weakest, and almost certainly the most that could have survived the political process intact. The fight over the next two years will determine whether the agency-level rule survives the courts and the next administration.

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