I'm just going to throw this out there knowing that a certain type of reader will scoff.
First, the EPA sets two competing requirements: lower emissions and higher mileage. Do they have any engineering expertise that proves this is even possible? My guess is not just no but hell no. It's also possible that the EPA can get away with this by playing the evil, greedy corporation card saying, "The car companies don't want to do this because they are greedy," and a certain type of person will believe it. So, if you're a manufacturer trying to sell a product, which of these two requirements is going to sell better? I can pretty much guarantee that the consumer doesn't give a rat's ass about emissions when they could be saving money on gas which may also be artificially expensive.
Second, it's entirely possible that the EPA has created unrealistic if not unattainable requirements for auto manufacturers not because they have any real scientific or engineering expertise that it's possible but in a thinly-veiled long-con attempt to drive these companies out of business. Kafka would say, "Damn, wish I had thought of this." The consumer is never going to pay more money for less product unless they are forced to. Brow-beating them into "saving the planet" doesn't work when it's costing the individual a lot more money.