Trump says he is rolling back Biden-era US fuel economy rules for cars

A formal rollback enacted through regulatory channels would likely benefit traditional automakers and suppliers dependent on internal combustion engines, while putting downward pressure on EV-focused manufacturers and battery suppliers that had priced in stricter efficiency mandates.

If the announcement remains rhetorical without legislative or regulatory follow-through, markets would plausibly treat it as political positioning; automakers would continue hedging across both EV and ICE portfolios, leaving sector valuations relatively stable pending clarity on actual policy implementation.

A legal or political battle over rollback authority—such as court challenges or Congressional intervention—would extend regulatory uncertainty and likely increase volatility in automotive and clean energy equities as investors recalibrate exposure to competing policy outcomes.