Electrohydraulic valves have seen increasing use in all fluid power applications, especially in the automotive field. This includes automobiles, heavy equipment, and all mobile equipment. Pulse width modulation (PWM) has been, and continues to be a popular choice for control in many applications. Common uses for such valves are in transmissions, anti-lock brake systems, electronic fuel injection systems, and active suspension systems. These broad application areas usually all have one common application limitation, use of a low force electromechanical valve actuator. This is most commonly an electric solenoid and often imparts less than one pound of force to actuate the valve.This use of low force valve actuators has thus magnified the effect that contaminants have on the valves. Compounded with this is the varying nature of field induced and generated contaminants. This paper thus investigates these type valves at length, provides analytical descriptions of and experience gained from many hundred experimental studies into valve contaminant service life, and presents data on the development of a new test contaminant which simulates that found in high mileage automotive-type transmissions.