On Saturday 26 September, President Trump posted that he had approved new Corporate Average Fuel Economy standards, replacing the Biden-era rules he describes as an "EV mandate." Transportation Secretary Sean Duffy followed with his own post: a "major victory for America's auto workers is COMING MONDAY."
The number that matters is 34.5 mpg, a fleet-wide average by model year 2031. The rule it replaces required roughly 50.4 mpg by the same year.
That is a cut of about 31% — and as of this writing, the actual rule text has not been published.
What Is Actually Changing
CAFE has worked the same way since 1975: automakers are not told which cars to build, they are told what their sales-weighted fleet average has to be. Sell enough inefficient vehicles and you must offset them with efficient ones, buy credits, or pay penalties.
The administration's December 2025 proposal — which is where the 34.5 mpg figure originates — does four things:
- Resets the baseline retroactively. The model year 2022 standard is revised downward, and stringency then rises by between 0.25% and 0.5% a year through 2031. For context, that is a rate of improvement slower than ordinary engineering drift.
- Kills credit trading from model year 2028. Today a manufacturer that overshoots can sell credits to one that undershoots. Removing that market removes a revenue line that has been worth real money to EV-heavy sellers, and removes an escape hatch for everyone else.
- Reclassifies crossovers and small SUVs as passenger automobiles rather than light trucks. This one sounds technical and is not: the light-truck category has always carried a softer target, and moving vehicles out of it normally tightens the maths. Against a 34.5 mpg ceiling, it mostly rearranges which column the slack sits in.
- Rewrites the compliance path for 2029-2031 down to a 0.25% annual step.
The Government's Own Numbers Cut Both Ways
This is the part worth reading carefully, because the administration and the agency are not quoting the same figure.
The political claim: DOT's December announcement put savings at $109 billion over five years and roughly $1,000 off the price of a new vehicle.
NHTSA's own modelling, as reported by Reuters, says:
| Metric | NHTSA estimate |
|---|---|
| Average upfront vehicle cost | −$930 |
| Additional fuel burned by 2050 | ~100 billion gallons |
| Additional fuel spending by 2050 | $185 billion |
| CO2 emissions | ~+5% |
So the agency's figure for the sticker saving is $930, not $1,000. And the same agency projects that buyers recover that $930 once and then pay $185 billion collectively at the pump over the following quarter-century.
A rule that takes $930 off the purchase and adds $185 billion to the running costs is not a cost cut. It is a transfer from the fuel budget to the showroom floor — and the showroom is where the politics lives.
None of this is a leak or a critic's estimate. It is in the regulatory record the administration itself produced.
What It Means for Product Plans
For anyone reading this from a planning function rather than a political one, the operative fact is not the mpg number. It is regulatory instability.
Powertrain programmes run five to seven years. The 50.4 mpg target shaped capital allocation decisions taken in 2023 and 2024 — hybrid architectures, battery supply contracts, plant retooling — and those decisions cannot be unwound by a social-media post. Automakers that built toward the stricter rule now hold assets sized for a market the federal government has stopped requiring.
That is not automatically a loss. Three things blunt it:
- Export markets have not moved. Europe and China are still tightening. A US-only relaxation does not relax the product plan for a company that sells globally.
- California and the Section 177 states have their own authority, and their own litigation history. A federal floor is not a national ceiling.
- The rule will be challenged. A retroactive revision to a model year that closed four years ago is an unusually large target, and the projected emissions increase sits in the agency's own file.
Former Transportation Secretary Pete Buttigieg's line — that the move will "accelerate what [Trump] has already been doing: handing the clean tech future to China" — is a political framing, but the commercial version of it is harder to dismiss. Chinese manufacturers are not slowing efficiency development because Washington relaxed a target.
One Correction Worth Making
Both the administration's framing and much of the coverage use the phrase "EV mandate." As Al Jazeera notes directly: no federal law requires Americans to buy electric cars, and none bars the sale of petrol-powered ones. CAFE sets an average; it does not set a product.
That distinction matters for anyone trying to read the actual commercial signal out of this. What changed on Saturday was the slope of a compliance curve — not a ban being lifted, because there was no ban.
What to watch: the formal unveiling on Monday 29 September and, more importantly, the published rule text. Until that lands, the 34.5 mpg figure is the December proposal's number, restated by the President. The final rule may or may not match it, and the difference between "approved" and "filed in the Federal Register" is where the litigation clock actually starts.
