J. Severyn writes:

The red box is also where high peak internal cylinder pressures are
encountered. The combination of the high temps and high internal pressures
are detrimental to the life of the engine, and tend to thin out the owner's
wallet very quickly. (or worse)

The same power output (but less than max power) can be attained ROP and LOP,
but the engine runs cooler and more efficiently LOP. But the pilot must
ensure he/she is LEAN enough to stay out of the red box.

If the pilot needs maximum power (say during max. gross weight takeoff),
then ROP operation is normal. But again, the pilot must ensure he/she is
RICH enough to stay out of the red box. Fuel economy is not an issue during
the takeoff......just max power to clear obstacles and safely climb to a
cruise altitude.

It seems, then, that the only reason to cross through the red box is
to improve fuel economy (?).

Overall, based on some conflicting stuff I've read in various places,
I've managed to distill a handful of fairly common recommendations:

- Use full rich on take-off and landing, unless you're at a really
high altitude

- At other times mixture isn't critical, but leaning slightly with
altitude saves fuel and provides more power.

It sounds like you can fly around with full rich all the time if you
want, except that you'll waste fuel and potentially dirty the engine
in time. More reasonably, you can lean a bit as you get higher in the
air, reducing fuel consumption and possible dirtying of the engine.
Tweaking the mixture beyond that can save more fuel and (perhaps)
somewhat reduce engine wear, but it requires a lot more attention.

Does this more or less look correct?

Mxs, if you ever make it to the San Francisco Bay area, look me up. I'll
get you a few hours in the air where you can try it out yourself.

It's unlikely I'll be anywhere near KSFO in the foreseeable future,
except in simulation. If you're on VATSIM and you spot a Baron with
tail number N9119E or a Boeing Business Jet 2 with tail number N9119F,
that's probably me. At this particular instant I'm parked at Gate 10
at KSAN, but not for long, as I'll be returning to KPHX shortly.

--
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