A sensing apparatus for determining a property of a fuel such as a gasoline and ethanol blend known as flex fuel includes an acetal plastic tube with an inlet, an outlet and a fuel passage in between. One property of the fuel is a dielectric constant. A pair of sensing plates are placed on opposite sides of the tube leaving the fuel passage unobstructed. A processing circuit on a printed circuit board (PCB) is located near to and is connected with the sensing plates. The circuit applies an excitation signal, senses a capacitance, and generates an output signal indicative of a property of the fuel. The sensed capacitance will increase with increasing concentration of ethanol in the fuel flowing through the passage. A shield for reducing EMI surrounds and encloses the sensing plates and the PCB. An interface connector allows the sensing apparatus to output the capacitance indicative signal to an engine controller or the like.