wrote in message
.. .

On 3-Jan-2009, "Viperdoc" wrote:

I suspect that both companies are not interested in doing any testing or
changing their many year old operating instructions in order to limit
their
liability exposure.

You may be exactly right. Somewhat irrelevant for me, since my 1978 Cessna
172N doesn't have an EGT gauge or cylinder head temp gauges. My POH says
to
lean until the tach drops 25 to 50 RPM, which I've read is supposedly
somewhere slightly lean of peak. My partners say they lean until the tach
drops off, then twist the mixture knob back rich a couple of turns. I do
the
25 RPM drop-off method, but I've always been worried I might be causing
damage to the engine, based on what I've read in some of the on-line
articles people on this group recommended. Or maybe my partners are
damaging
the engine by doing it their way, if not just wasting some gas. I wish
there was a way to be absolutely sure.
Scott Wilson

I don't know about the 172N, but the manual for the 152 had a very similar
recommendation for lean operation--but it was stated for 60% power (and was
obviously appropriate for less than 60% as well).

What does your POH say about the power setting?

Peter