A fuel conditioning device (1) for attachment to a fuel line (5) of a fuel combustion machine to improve combustion efficiency thereof. The device (1) includes a frequency controlled signal generator (14) powered by a power supply (2). The frequency controlled signal generator (14) has a first output being connected to the first output wire (8) coiled around the fuel line (5) for producing a first shark dorsal waveform voltage signal (15) oscillating at a predetermined frequency. The frequency controlled signal generator (14) has a second output connected to the second output wire (9) coiled around the fuel line (5) for producing a second shark dorsal waveform voltage signal (16) oscillating at the predetermined frequency. The second shark dorsal waveform voltage signal (16) is an inverted mirror signal of the first shark dorsal waveform voltage signal (15).