Brad, as best we can tell, in all the literature and on the dyno test stand, there is no way you can get detonation when LOP, or not in any N/A engine, and even in a turbocharged engine if run LOP properly.
When I am there next, which will be quite often in the near future doing reall serious detonation testing, I will have a go. At 30" 2500 and 10dF LOP I think on conforming fuel there will be none. And we will have to abuse it a little.
The most detonation prone mixture is one around 50dF ROP. Does that number sound familiar.
Have your CHTs at 370 in a NA engine and LOP......not a chance.
Having said that, it may still not be optimal for the engine. If you are LOP, and not far enough LOP say high power 85% and only 10dF LOP and your cooling system is good, or you are in a cold climate, you could consider this abusive. Not going to crater your engine in any time soon, but the concept of stress and temperature in combination being the enemy of longevity plays its hand. So just because you have forced the CHT down by being in Alaska in winter, and abusing the engine, I would say that is sub optimal long term would you not?
If you did the same thing at 40-50 ROP and asked me which would I prefer of the two, it would be a no brainer as the ICP's and CHT's would all be lower. If you were conducting ops requiring high power and ROP, then 200+ or full rich is the answer. If not throttle hacking, then 80dF LOP.
The APS Landmarks graph paints a good picture.
Bob, I will take that as you meant to say "Choose" and I do agree with you
, the better way to say it would be
I'd say the most important use is if you follow Lycoming's advice to not lean insufficiently enough above 75%.