I'm not sure if there so much disagreement here, but rather looking at temperature from different viewpoints. All engines, air, water or oil cooled are designed to run at range of operating temperatures. If it doesn't run there bad things happen. Letting engines just sit and run isn't good. I'm sure we've all seen the cop cars sitting with hoods up in the summer to cool them. One of the things designers can overlook is the oil not only lubricates but carries heat away from vital areas. For example, a good friend explained how that was a major contributor in FD failures.