Abstract: A fuel conditioner of the type having a housing defining an inner chamber for receiving a filter element, inlet and outlet ports in the housing for establishing a flow of fuel to and from the chamber, and a heater for raising the temperature of the fuel between the inlet and outlet ports. The improvement comprises a baffle plate situated within the housing between the inlet and outlet ports, for directing substantially all the flow of fuel as a thin layer against a selected interior portion of the housing. The heater is situated on the housing exterior adjacent the interior portion of the housing containing the baffle. The fuel passing through the thin passageway therein reaches its highest velocity in the conditioning unit. Particularly if the flow boundary area defined by the housing and the baffle plate is large compared with the volume of the passageway, very high heat transfer from the heating element to the fuel in the passageway is achieved.