Read this
http://www.anl.gov/PCS/acsfuel/prepr...03-98_0216.pdf and there was another one i read that said that the magnets only work if u have the south side towards the fuel so the other ones they tested most likely had the north sides towards the fuel or the north and south witch the study says cancels the effect of the south side anyway, and it only reduces the viscosity or surface tension of the fluid(just like acetones supposed to do which increased my fuel economy by 5mpg in town)