A magnetic fuel conditioner according to the present invention includes an inner pipe, an outer pipe surrounding the inner pipe with sufficient clearance that fuel can pass between the inner pipe and the outer pipe, a plurality of magnets placed inside the inner pipe with like magnetic poles facing each other, and a plurality of mild steel disks placed between each pair of magnets. In a preferred form, the inner pipe and the outer pipe are made of stainless steel. An outer sleeve of mild steel surrounds the outer pipe. In a preferred arrangement, each of the plurality of magnets is cylindrically shaped to tightly fit into the inner pipe and is in the range of from about 9000 gauss to about 10,000 gauss. Typically, the plurality of magnets comprise neodymium. In such an arrangement, each disk of mild steel is approximately one quarter inch thick and approximately the same diameter as the magnets in the plurality of magnets. There are two stainless steel cylinders of approximately the same diameter as the cylindrically shaped magnets. One of the stainless steel cylinders is placed in each end of the inner pipe and secured to retain the plurality of magnets within the inner pipe. A magnetic fuel conditioner according to the present invention is especially well suited when the fuel to be conditioned is diesel fuel.