Keep fuel economy rules with Transportation, not the EPA
What the document says“Any EPA limits on carbon dioxide emissions, even if authorized under the Clean Air Act, must support and work in harmony with DOT standards”
The chapter says environmental limits must not override or usurp the transportation department's role under the 1975 energy statute, and offers as an example that the environmental agency could regulate air conditioning systems and leave engine standards to transportation.
What the document actually says“Any EPA limits on carbon dioxide emissions, even if authorized under the Clean Air Act, must support and work in harmony with DOT standards”
Any carbon limits must fit with the transport rules. They must not override them.
Two agencies both affect car rules. One covers mileage, one covers pollution. The book says the mileage agency should lead.
Rescission of the Greenhouse Gas Endangerment Finding and Motor Vehicle Greenhouse Gas Emission Standards Under the Clean Air Act
2026-02-18 · 91 FR 7686
The Federal Register summary of this final rule of February 18, 2026 records the Environmental Protection Agency rescinding the 2009 findings of contribution and endangerment and repealing all greenhouse gas emission standards for light-duty, medium-duty and heavy-duty vehicles and engines, on the agency's reading that section 202(a)(1) of the Clean Air Act does not authorize standards set in response to global climate change concerns. That removes the federal carbon limits on vehicles that the passage says must not override the fuel economy standards Congress assigned to the Transportation Department, so the clash the chapter describes no longer arises. The fit breaks down because the passage assumes such limits continue and asks only that they support and work in harmony with the Transportation Department's standards, offering air conditioning systems as an example of what the environmental agency might still regulate, while the rule concludes the agency has no authority to set vehicle greenhouse gas standards at all. The rule states no relationship between the two agencies, and neither the 1975 energy statute nor the Transportation Department appears in what the site holds, which for this document is the rule's own summary rather than its full text.
The same rule of February 18, 2026 lifts the federal climate limits on cars. The passage said such limits must not override the mileage rules Congress set. With the limits gone, that clash no longer comes up. But the rule goes further and says the agency had no power to set them at all.