Temps killing engine
 

Anyone know if it is only high temps that will kill the engine or is it possible to "overstress" it (to the point of failure) even though it is running at an acceptable temerature?

Don't let the oil temp drop. The lack of viscosity might damaged your engine.

If you mean overstress = overrev, then yes, that is possible also. The 109 is particularly susceptible to that.

Thank you for the replies.

+1

It should be between 50 and 80-90 degrees for normal operation in most aircraft. Lower than 30-40 and the oil could be so thick that the pressure can damage components (the Blenheim's prop governors are notorious in this regard). Higher than 100 and it breaks down and stops providing sufficient lubrication, which can result in overheating and an oil fire.