Blood-magneto suction drums! Fuel polarizers! The history of flake-o miracle fuel-economy devices probably stretches back as far as the invention of the motor vehicle. Here's an interesting 1968 article on a comparison test between a number of such devices, scanned and put online by the good folks at The Olds Zone (a Cutlass was used for the tests). Spoiler: no miracles discovered. But we got a nice perpetual-motion machine for ya!
Test Report on Those Gas-Saving Gadgets [The Olds Zone]
Own The Smart Fuel Injection System Patent For Only $5M! [internal]