I'm not sure I agree with the thermostat theory. Once the car has driven about 1 or 2 km in current Brisbane conditions, the thermostat will/should be open. Thermostats (engine) rarely just fail and then close mid drive. It's more a case of them never opening fully or jamming open or closed. If jammed closed from the start, you'd be overheating everywhere. Of course, if that pesky auto transmission thermostat has failed then all bets are off.
It wouldn't hurt (except your wallet) to replace it. I'm fairly paranoid about coolant temps, but I'd be closely monitoring it for the time being to see what happens - especially if you have a monitoring system better than just the dash temp gauge.
Last edited by Brissyjohn; 12-17-2012 at 04:00 AM.