Is the oil travelling only in one direction, or is the fluid moving forward and backward with respect to the channel? Because of the nature of video being many images taken per second, we could be seeing an illusion of the gears moving forward and backard and forward again, or event moving in the opposite direction they are actually moving.
Is there a channel toward the top of the diagram toward which the oil is moving or to the sides? Is the channel at the bottom extending down and away from the viewer?