2nd half of my answer
In piston rings this means that wearing in to a perfect fit that seals oil
and combustion gasses with an acceptable wear rate requires controlled
conditions lest one of the components wear to a shape that will never be
right. During this period, especially in the first seconds or minutes of
operation, the lubricant in that area must be able to carry away enough
frictional heat to prevent destructive high local temperatures from
happening. We're talking at the microscopic level here.
A light weight oil will move to the place where it can cool effectively more
easily than a heavy oil. Once there it does it's best job of allowing the
surfaces to touch and wear in by losing viscosity through heating so it can
penetrate. It also helps by vaporizing, a process that draws away much heat
from its surroundings, familiar to us in the boiling of water in a pot on a
hot stove burner that might otherwise melt the pot. Synthetic oils need to
go to higher temperatures in the 400-600 degF range for this to happen. In
this range we begin to see property changes for the worse in metals like are
used in piston rings. A petroleum oil that breaks down at lower temperature
absorbing heat from the metal may be a better choice.
Since the jury seems to be out on synthetics for break-in I would favor
recommendations that are supported by well recorded data and experiances.
I'd tend to stay with light viscosity (at high temps as in the "30" in
10W-30) unless the ring manufacturer said something specifically different.
They would know.
Ed Weldon
> ----- Original Message -----
> From: "Tom Neimeyer" <Tneimeyer@houston.rr.com>
> To: "Ed Weldon" <23.weldon@comcast.net>; <land-speed@autox.team.net>
> Sent: Friday, October 20, 2006 5:39 PM
> Subject: Re: Engine Assembly Lube
> > One question, I have heard some say "never use synthetic for break in"
and
> > others say it's OK, what are the lists thoughts?
> > Cheers, Tom
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