Abstract: A fuel conditioning device for installation in a fuel supply line of an internal combustion engine comprises a housing having a cylindrical ferromagnetic wall defining a fuel flow path and, in the flow path, a tin alloy body and a magnet adjacent and downstream thereof. The tin body has fins extending perpendicularly from a central diametrical spine and the magnet is diametrically disposed along the housing and has poles on opposite sides which face the housing wall so that substantially all fuel flows between the faces of the magnet and the wall. Apertured distributor plates can be positioned across the flow path to induce turbulence in the fuel thereby improving washing over the alloy.