A system and method for determining whether a working fluid being used in a machine is near its failure point. The system includes an impedance/admittance sensor having a flow chamber through which the working fluid flows and a pair of spaced apart electrodes. A function generator generates frequency signals at certain frequencies over a range of frequencies and a sensor circuit receives the frequency signals and provides the frequency signals to the electrodes, where the conductance of the working fluid creates a measurement signal in the sensor circuit. A processor is responsive to the measurement signal and generates a relationship between the frequency signals and the measurement signal that is indicative of a contamination level of the working fluid.