There are vortex devices that do work but what you saw advertised is nothing
more than a scam for the gullible. My grandfather got one for his Ford
pickup in about 1948 and could barely get the car to run with it installed,
notwithstanding the demonstration they put on with increased idle speed,
etc.

The vortex tubes that DO work are devices that by extreme centrifugal force
separate compressed gases into hot and cold components. They are used for
cooling air-supplied masks for painting with toxic paints, etc. They put
out a stream of hot air at about 140°F and another stream of cool air at
about 65°F, which is also pretty dry so if you are sweating, it feels really
cool. They are not very efficient but they are compact and effective. Safety
equipment suppliers sold them in the early 80s. I haven't seen one in a long
time.
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George Downs Bartlesville, Heart of the USA!