I'm not sure on what, if any, scientific issue/s we differ any more, oggers and Eddie, so I'll frame the discussion a different way.
Which of these mixture settings will, in your view, be better for a piston engine's longevity:
- 30 degrees F Rich of Peak
- 30 degrees F Lean of Peak
Balloon, we disgree on the APS hypothesis that exhaust gas does not affect valve temperature...unless you have had an epiphany.
As you keep asking, it's 30 lean. I'm not aware that anyone has ever argued 30 ROP is the best place to run an engine for longevity. Sorry to shoot your fox.