No thermostat? I always thought that CAUSED the engine to run hot. Once the fluid reaches maximum hottness, the only cool factor was when it raced through the radiator. The fluid didn't have a chance to sit and rest a while. You said that super coolant had a boiling point of 375 degrees.I don't know what the "normal" operating temperature is for your motor,
but I think it is well below that. Everything everybody has said is right on target. The only thing I might suggest is a bad head gasket. They sometimes cause curious things to happen.
