If your worried about fuel milage buy a prius. All of these snake oil remities and worthless gadgets for increasing fuel milage are annoying and 99% of the time the gadgets cost more than any savings that will ever be seen in milage increases. It reminds me of magnets on the fuel line will help improve milage aligning the fuel molecules for better atomization or who can forget the tornado contraption. 100's weigh 5100#+ stock, as aerodynamic as cinder block and a 4.7l v8. I heard if you piss in your radiator you will increase fuel milage by 5% because piss has better cooling properties than water and therfore the engine will run in the proper temp range for proper fuel combustion, aligniment of antifreeze molecules and even proper tire wear.
I betcha someone will try this...