The Hyco cold vaporizer. This is a cold vapor unit which can give 50-80 % fuel mileage plus, if done to the instructions on the video.
By George Wiseman of Eagle-Research.
This device can easily be replicated from parts from a local hardware and automotive store. Just by watching this video you will get a good understanding how to do it.
Warning, if you make this, do adjust fuel mixture and take fuel out of the fuel system or lean it down a bit. You will have extra vapor which will richen your fuel system due to the extra vapor from this unit, this is why it is important to adjust the fuel.
If you have a EFI (fuel injection) vehicle you need the oxygen sensor modification or a manual adjuster control otherwise, this or other fuel savers won't work.