Abstract: A magnetic focusing fuel treating assembly coupled to the fuel line of an internal combustion engine. The assembly includes a ferromagnetic plug that extends through the inner hole of an annular permanent magnet. The plug and the magnet are separated by a precise annular gap. Attached to the magnet and located at the ends of the plug are a pair of ferromagnetic end plates. The magnet emits a focused, concentrated magnetic field that flows into the fuel. The focused magnetic field has been found to improve the performance of the engine, demonstrated by improved fuel economy and reduced emissions.