Apparently, it's possible to get 200+ mpg without HHO, fuel line magnets, super carburators, fuel pills, acetone, hydroxy boost, hydrogen, fuel atomizer.catalyst -- you name it. All it takes a light weight, aerodynamic car with a very efficient Diesel hybrid engine.
First drive: 261 mpg Volkswagen XL1
"this diesel plug-in hybrid recently received a mind-boggling rating from European authorities of 261 mpg, far and away a record"