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Date: Tue, 03 May 2005 14:05:48 -0400
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From: Walter Atkinson <walter@advancedpilot.com>
Subject: Re: [LML] Re: Hard Facts About Engine Break-In

Gary:

Well done!  I would only add that mineral oil does break down at lower 
temperatures than the other oils.  That could be a disadvantage during 
the high temp times of most break in periods.  Basically, I feel like 
you hit the nail on the head.

Walter


On May 3, 2005, at 10:49 AM, Gary Casey wrote:

The information I have comes from a number of experts in the field, 
most oil
companies and engineers at GM and Mercury Marine.  I hope they are 
facts and
not, as Larry so aptly said, "..too early for the facts to be  
factual.."
The narrative below contains a good number of ", indicating that the 
facts
may not be factual at all.

I'm not sure anyone knows precisely what happens during "break-in", but 
the
idea is to wear off the peaks of the roughness mountains until the 
landscape
looks more like mesas surrounding oil-holding canyons.  Take too little 
off
and the engine might continue to wear, take too much off and there 
might not
be enough oil trapped in the surface.  I sort of believe the above
description.

So-called "mineral" oil lubricates "better" that dispersant oil because 
the
additives whose purpose is to keep contaminates in suspension are not 
good
lubricators.  The dispersant (detergent) additive takes up a significant
portion of the oil.  Presumably you need "good" oil during break-in to
prevent galling (one mountain welds itself to a mountain on the mating 
part,
pulling the mountain out by the roots, creating all sorts of mayhem).
However, in the last 80 years the technology of cylinder and ring 
surface
finishing has progressed to the point that it may not make much 
difference
what oil is used.  I definitely like Walter's method of running high 
power
and lean in order to reduce the peak pressure and spread it out over 
more of
the stroke.

I'm sure the requirements from Lycoming are good intentioned, but...if 
you
were the suspicious sort you could see a very strict break-in procedure 
as
one way to protect the manufacturer from us ("burns oil?  did you keep
mineral oil in for exactly 40 hours?  It was 39?  Sorry, we can't 
help.").
What incentive does Lycoming have to change their requirements?  And
finally, the auto industry has spent a lot of time and money perfecting
surface finishes that eliminate the need for any special treatment 
during
the break-in period.  The automotive and aircraft people do talk to each
other and the rings are made by the same people, so I suspect that 
strict
break-in procedures might have outlived their usefulness.  Except my 
engine
is so expensive, it doesn't hurt...and so it goes.

Gary Casey


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