My radiator was professionally cleaned and I put the Zerex concentrate in. Car (1989 300SE) is running over the 80 mark on the gauge and closer to that next line. NOTE: Today was about 90 and I was running the AC. I just rebuilt the head due to overheating and blowing the head gasket. Car is running great, but I want to make sure that I don't overheat again since I am planning to take it on a 200 sojourn over the weekend. Maybe I am being paranoid, but I want to make sure all is ok.