Vaporizers
Gasoline engines can be modified to run on tractor vaporizing oil (TVO) and such engines were once common in tractors. The modifications include a reduced compression ratio and a carburetor with a vaporizer. The vaporizer uses heat from the exhaust to vaporize the fuel. Widespread adoption of diesel engines in tractors made the use of tractor vaporizing oil obsolete.
Read more about this topic: Carburetor