AND 36 mpg to boot. That was back in 1976. Doesn't look like we've come very far in the last 38 years. (As far as mpg's) Modern Cars should be getting much much better mpg's if you ask me.
Ethanol. That's the problem, or at least the major one. It takes nearly twice the amount of ethanol to do the same "work" as gasoline. And when the piss you buy at the pump is 10% ethanol, it's gonna take more of it to do the "work".
Also, the enviro whack jobs think you should be able to breath the exhaust on today's cars. In a lot of cases, tighter emission standards equate to less volumetric efficiency.