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From: dennis@vrdxhq.UUCP (R. Dennis Gibbs)
Newsgroups: net.auto.tech
Subject: Re: Syn Oil and Breakin
Message-ID: <2316@vrdxhq.UUCP>
Date: Tue, 3-Dec-85 13:16:20 EST
Article-I.D.: vrdxhq.2316
Posted: Tue Dec  3 13:16:20 1985
Date-Received: Fri, 6-Dec-85 06:37:40 EST
References: <746@drutx.UUCP>
Organization: Verdix Corporation, Chantilly, VA
Lines: 56
Summary: Why it is necessary to break an engine in before using a synthetic

In article <746@drutx.UUCP>, pagiven@drutx.UUCP (GivenP) writes:
> I have heard from more than one source now, that before using  syn-
> thetic  oil,  the  engine  should have 6K to 8K miles so the engine
> could properly "break in," "seat," or "become seasoned."
> 
> What exactly do these terms mean, anyway?  Is it necessary  for  an
> engine  to wear out to a certain degree before the process is stop-
> ped with a changeover to synthetic oil?
> 

It means that when an engine is brand new, internal parts (seals, piston rings,
etc.) do not fit well together on a microscopic level.  It takes some time 
before these parts can "wear" down so that they mate perfectly with their
corresponding parts.  Until this break-in has occurred, it is not uncommon
for a brand new engine to consume more oil than normal.  As the engine is
used, the surfaces "wear in", giving a closer fit and a better seal.  This is
why most owner's manuals usually have a paragraph suggesting that the oil
level should be checked frequently during the break in period.

> It would seem to me that as  an  engine  wears,  tolerances  become
> greater, that is, parts fit more loosely and thereby no longer pro-
> perly seal.  For instance, oil leaks past rings into the combustion
> chamber, oil leaks past valve guides, gasoline and burnt byproducts
> blow past the rings into the oil, tappets start making noise, etc.,
> etc., all to a greater degree in engines that have more wear.
> 
> I had 400 miles on my 1981 Buick when I changed to  synthetic.   It
> now has 95K more miles on, with no increase in oil consumption.  It
> uses about 1 quart every 4K to 5K miles now as it did when  it  was
> new.   Should  I  be  concerned  that  my engine was never properly
> "broken in?"
> 
>  Paul Given             {ihnp4, houxe, stcvax!ihnp4}!drutx!pagiven

Synthetics have a higher film strength and lower coefficient of friction than
do regular oils.  Thus, if synthetic is installed in a brand new engine, it
may impede the break in process, by not allowing the internal parts to "wear"
down so that a closer fit and a better seal (for oil control) is achieved.

Every engine (even the same brand and type of engine) differs in the length
of the break in period.  Some engines need only a couple hundred miles to
break in properly, while others need a few thousand.  

Your experience with your Buick indicate that the engine was  broken in
sufficiently when you put the synthetic in.  I don't think you have a thing
to be concerned about, an engine that has 95K miles and still gets 4 - 5K
miles to a quart of oil is very good indeed.

The reason I recommended a break-in period of 6 - 8K miles is to allow even
the most "stubborn" engines to break in completely.  Since there is no way to
really predict or name an exact mileage figure for break in, it is safer to
assume the engine takes several thousand miles to break in.  Also, at 6 - 8K
miles, the engine is still new enough so that it is unlikely that significant
carbon deposits will have built up.

                       Dennis Gibbs