A thermostatic air control for assist air to a fuel injector utilizes a bi-metallic ring to seal the air inlets when the engine temperature has increased. This in effect prevents the flow of assist air when the engine is warm and the need for assist air is not required. The bi-metallic ring can have either a positive or negative temperature coefficient and is positioned either on the inside or the outside, respectively of the air assist shroud of either a top or bottom feed fuel injector. A small orifice having a predetermined size and discharge coefficient provides a constant air flow to the output of the injector.