While I'm doing the radiator i thought I'd do the thermostat too. I purchased a gasket that came with a small coating of rtv on one side. The old t-stat had no such gasket but instead a plastic ring around it with a notch that held it in place. Do I need to use this new gasket or just use the one from the old t-stat. I'm thinking of using the old gasket and smearing some high temp rtv on the housing. Is this right?