I have 04 disco with re-man short block from AB with top hat liners. When doing the rebuild I used PEL500110 thermostat. Driving temps are now 184-193. I think they use to be 206. So it certainly seems to help.
seventyfive said:just remove as much coolant as you can. top up with distilled water and organic coolant (i prefer Motul inugel) bleed system. drive a week, and repeat. unless you're having issues with the heater core i.e. blockage, you shouldn't need a 'treatment'.