A technique facilitates control over flow of fluid in a variety of well applications and other applications. A flow control device is used to automatically control flow of fluids based on viscosity of the fluids. For example, the flow control device may be used to automatically allow flow of oil while blocking flow of gas and/or water. According to an embodiment, the flow control device comprises a production circuit and a metering circuit. The production circuit and the metering circuit cooperate to allow flow of a well fluid with a first viscosity and to block flow of well fluid when the well fluid has a different viscosity, e.g. relatively lower viscosity.