The Pogue Carburetor. The “200 mpg” carburetor that started all the legends.

The inventor himself never claimed the carburetor (which was actually a fuel vaporizer that used exhaust heat to vaporize fuel) would deliver 200mpg. But he did claim the rumor caused him no end of grief - such as his shop being broken into by those who (apparently) wanted to steal his invention on several occasions.

The patent has long since expired, so anybody wanted to build one is free to do so. Even so, the myth that the technology was bought up then buried persists.

Interestingly, in 1927 every Model T Ford came fitted with fuel vaporizers, and the Fordson tractor did as well. Did they work? Sure. Did they get 200mpg? Not even close. The vaporizer did however allow lower grade fuels (eg. kerosene) to be burned, so there was at least some truth to improved economy in the myths.