Posted for George Braly <gwbraly@gami.com>:

Dan,

When I teach IA certificate renewal classes,  I do a little quiz.

It turns out that about 95 out of every 100 mechanics in the room believe
that a "lean mixture" is one that is about 25F ROP.

None of them have any experience with operations that are ACTUALLY lean of
peak - - as opposed to  just  "not rich enough".

One mechanic recently made a comment on the AVSIG forum on CompuServe that
all of the engines run "too lean" burned up...

One of his customers pointed out that he had just disassembled his 1800 hour
TIO-540 Lycoming and had commented that that was an exceptional clean
engine.

That engine had been operated from the 1000 hour point out to 1800 hours all
lean of peak.  For the first 1000 hours of its life, it was run ROP and all
six jugs were changed, some more than once.  From 1000 to 1800 no jugs were
changed. The mechanic in question  was intellectually honest about the matter and
confessed that in his 20 something years - - that was the FIRST AND ONLY
ENGINE he had ever had in his shop that he ACTUALLY knew had been run LOP,
as opposed to having been run "... not rich enough."

This is VERY typical of engine people and engine shops.

Regards,  George