The present invention is directed to a dual fuel system and a dual fuel system assembly where liquid LPG and diesel are mixed and then distributed via the common rail to the combustion chambers. The liquid fuel mixture remains in a liquid state and under pressure for introduction to the combustion chambers. With the preferred embodiment of the dual fuel system, only minor changes are required to the diesel engine without altering the manufactures specifications and voiding the manufacturer's warranties. The resultant combustion of the liquid fuel mixture provides a cleaner emission and relatively cheaper vehicle operational costs.