I am not a professional mechanic. This is not professional advice. I am merely a backyard mechanic. Work on cars at your own risk. If your temperature gauge is showing that your engine is running too cold it will not run well. Typical engines need to operate between 195 and 205 degrees. If your operating temperature is below 195 your thermostat is probably "stuck open" and needs to be replaced. In this episode I not only explain the importance of correctly operating thermostat but also show you how to replace the thermostat in a 2000 GMC Sierra SLE with a 4.8l Vortec engine.