Fluid pressure changes are imposed on selected interior surfaces of a plug passageway of a plug valve to create torque. In one embodiment perturbations are provided in selected flow surfaces of the valve plug to create turbulent boundary layer flow along such surfaces which generates a beneficial stabilizing torque tending to reduce or eliminate holding forces conventionally provided by mechanical parts such as detent mechanisms. In another embodiment, pilot holds between interior and exterior plug surfaces are used to alter the fluid pressure at diagonally opposite locations relative to the plug rotation axis to produce the stabilizing torque.