Your 1991-1993 Nissan 240SX is a liquid-cooled vehicle. This means that it uses coolant to keep the engine from overheating. In between the radiator and the engine is a thermostat that literally blocks the coolant and keeps it from flowing into the engine until the engine reaches its operating temperature. Through this process, the engine is maintained in its proper temperature for efficient operation. Complex as it is, the thermostat is considered a reliable cooling component. The flow of the coolant is controlled by a wax pellet. The wax melts as the temperature increases, allowing the liquid to pass. Lowering the temperature hardens the wax and this blocks the coolant. Through time, the effectiveness of your stock Nissan 240SX Thermostat will diminish and it has to be replaced with a new one. The Stant ST13967 Thermostat is just one of the thermostats being sold in the market today. Its performance is comparable to that of other brands. As far as affordability is concerned, its price is comparable to that of other products and you do not have to look for others anymore. We have a sufficient supply of these as far as our inventory is concerned. You can get a Stant Thermostat directly via our secure website. It is manned by competent sales specialists who will help you find your needed vehicle parts.