"Jose" wrote in message
. ..
[...] The old timers seemed to agree that:

1: at low power (say 65% or less) you can't hurt the engine by leaning to
peak EGT, but...

2: at high power (above that, including the 75% many like to fly at to go
fast) one should only lean if it's cold enough, and that the best thing to
do is run full rich if you're in doubt.

This runs counter to my understanding and practice. I lean (50 degrees
ROP) in cruise at all altitudes, including the ones where I can pick the
leaves off the trees, and I run 70-75% power. Running full rich is just
dumping a third of the fuel out the tailpipe.

Any opinions on Usenet about this?

I lean at all altitudes. Yes, you need to ensure you don't lean at too high
a power setting, but I believe that even there, for the smaller,
lower-compression engines overleaning isn't going to cause any harm to the
engine, you just won't get smooth operation.

Of course, the airplane I'm flying most often -- my own -- has a TIT gauge
to allow for accurate leaning at any altitude. I'm of the opinion that with
a TIT or EGT gauge, leaning at any altitude with cruise power settings is
the correct operational standard. But if there's no TIT or EGT gauge, I
think one can still lean without harming the engine. If one is worried
about overleaning, then just err on the rich side. ANY leaning is going to
be much better than flying around at full rich all the time.

Of course, in all cases I restrict my comments to cruise power settings.
Unless the aircraft manual and/or engine manual says otherwise, I don't lean
during full-power operation (and I don't fly airplanes that have a "climb
power" setting, so I have no opinion on that ).

As far as your "old timers" #2, I don't understand the rationale behind the
"if it's cold enough" part. If anything, one would only lean in *warmer*
weather, as that translates to higher density altitudes. It sounds as
though the suggestion has to do with overheating the engine, but the primary
damage from improper leaning, as far as I know, is detonation. Cold weather
does nothing to prevent this.

Pete