Save Big On Fuel Cost?????

  Has anyone out there heard about MPG-CAPS? 
I met a lady who says she's been putting these capsules in her gas tank for the past year and has save hundreds on gas.
Apparently these capsules are some sort of engine treament that increases the mileage your car gets and well as the life of spark plugs, valves and glow plugs. 
She gave me a  pamphlet that tells all these wonderful things about these capsules and your supposed to put them in the tank when you to fill up.
Anyone with any knowledge about this PLEASE let me know.