The Trump administration recently replaced the Obama administration’s strongest climate policy, the Clean Car Standards, with a significantly weaker rule. As justification, the EPA and National Highway Traffic Safety Administration gesture towards the possibility that consumers, by getting a car with better gas mileage, may miss out on features like higher horsepower and towing capacity. But even the agencies do not have enough confidence in their reasoning to include it in the main cost-benefit analysis. As our report explains, relying on this analytical gimmick contravenes decades of agency practice across administrations as well as the principles of basic economics. EPA and NHTSA's flawed analysis could ultimately cost Americans hundreds of billions of dollars at the pump.