There is quite a bit of research behind it. Some of the ebay sites do make some 'stretched' claims, but they will work. Recently i was looking at them, they arent cheap, although they should be because they are just magnets. Not sure of the polarity of them tho. Anyway i chose a random person off the list of people that have brought them off ebay and emailed him and asked if he had any improvements using it. I was lucky becuase hes actually doing some extensive research on them. In terms of fuel savings etc. i will be in contact with him soon and advise you of the results. However i do think you can expect fuel savings even if its just a few $ a week