Originally Ron Joseph will show up shortly and tell you 5600 is pushing it. I don't know if there is empirical evidence to support his claim for that precise number but I know that an engine kept at 5600 or less will live much longer than one that runs more than 6000. Simple physics says that.
Exactly my sentiments .....
It can't be explained better than that.
Add some unwanted, but common, detonation to the mix.
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