An on the fly fuel reformer device to produce variations in the autoignition and burning rate properties of a fuel by appropriate processing of some or all of a single fuel supply in its liquid form. The system includes a non-thermal plasma generator and/or a UV radiation source in contact with a fuel line so as to contact a multi-phase fuel in the line and dynamically modify the fuel to exhibit desired autoignition characteristics and burn rate such that the engine can operate with increased efficiency and lower emissions.