A separating device that includes a wedge that extends between first and second plates, with at least one of the plates being supported by a support device such as a bar. The single circuit includes a shift register, N determinators and decision logic. Use of a Fischer-Tropsch derived gas oil in a diesel fuel composition, optionally together with a detergent, to reduce andor clean up engine fouling is also described. The Multi Top-level Graphical Simulator can effectively isolate the operating systems andor hardwaredevice from the GUI-based application, and yet hide this simulation from the operating system andor hardwaredevice. In some instances, a heat exchanger may be utilized in parallel or series with the steam generator.