I've seen the temp gage in my truck climb above 200 (maybe 205-210) when running at slow speeds on steeper grades unloaded. Under normal highway driving even up steep mountain passes, the temp usually stays to the left of center on the gage (190-195). This is my first diesel truck ('04 with about 9K miles). The temp gage in my previous gas trucks never moved much under all operating conditions so I was curious if this is normal.