Could be because those old cars used carburetors and not fuel injectors. Back in the 50's I read about this guy that had developed a carburetor that would get 80 MPG on an 8 cylinder engine. For some reason it never showed up on the market. I am sure the guy and his relatives are still enjoying the money the oil industry paid him for his invention.
Don & Pat Allen - Texas Boomers - Honorary Oklahoma Boomers
2017 Keystone Sprinter 269FWRLS - 2017 Nissan Titan XD