Tim - checking the actual temp can tell you what thermostat you're running, just start checking the top rad hose cold until the temp jumps up .... if the temp is too low or high then you'll want to open it up and check the stat, otherwise why bother? checking the temps at various places is worth doing as a routine maint step, make sure the system is operating properly .... the one thing these trucks lack is a good temp gauge, they should always be checked against what's really happening to know what they're trying to say, originally mid range was usual, but they're all different
Bill
