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From: vince@fluke.UUCP (Craig V. Johnson)
Newsgroups: net.auto
Subject: Re: Mobil 1 oil
Message-ID: <140@vax2.fluke.UUCP>
Date: Wed, 12-Dec-84 13:16:00 EST
Article-I.D.: vax2.140
Posted: Wed Dec 12 13:16:00 1984
Date-Received: Sat, 15-Dec-84 00:42:30 EST
References: <1221@orca.UUCP>
Organization: John Fluke Mfg. Co., Inc., Everett, WA
Lines: 56

> 	As for Mobil 1 lasting 25000 mi between changes, don't
> you believe it. The oil molecules themselves might, but long 
> before then the oil will be polluted with minute metal particles 
> from engine wear and combustion blow by etc., especially if
> the engine is new or rebuilt. If you are are really concerned 
> about engine life, just do as the manual says. Oil and filter 
> every 7500 mi seems to be the norm (for Japanese cars at least).


The problem with running Mobil 1 for extended mileages is not with
particulate contamination (that's why you change your filter every
7-10K miles), but with chemical contamination mainly in the form of
sulphuric acid.  The acid is formed in the crankcase as a side affect
of combustion blow-by (gasoline contains trace amounts of sulphur).
All quality motor oils contain acid neutralizing agents and I'm sure
Mobil 1 is no exception.  However, this additive is consumed with time,
and fresh oil is necessary to replenish the additive.

My car is consuming about 1 quart of Mobil 1 every 2500 miles.  At this
rate I would consider changing the oil at over 20K miles, particularly
if I drove that many miles annually.  However, I do not drive more than
about 10K miles annually and between additive deterioration with time and
the fact that I get a lot of moisture build-up in the engine during the
winter, I have chosen to change my oil annually, usually toward the
latter part of the winter.

Two properties of Mobil 1 in addition to the extended change period are
worth noting.  First, the film strength of Mobil 1 is much greater than
conventional oils.  This allows the oil to protect much better even at
a considerably lower viscosity.  This leads to the other benefit.
Since the viscosity may be lowered, the engine expends less energy
sloshing it about, and this is the main reason behind the increased gas
mileage claims.  Also, the viscosity vs. temperature curve for the
synthetic is much flatter than for conventional oils.  This means it is
much thinner (and cars start easier) at low temperatures, and it is
much thicker (again better protection) at higher temperatures.  Mobil 1
also does not break down into the elements that cause sludge and
varnish deposits as do conventional oils.

By the way, a while back when I posted a message about Mobil 1, I
mentioned that the viscosity had been changed.  I have since checked it
out and now can report with certainty that Mobil 1 was originally 5W-20
and is today 5W-30.  I have no doubts that this was in response to
complaints Mobil received about excessive oil consumption.  The 5W-20
did indeed leak and/or get blown out the exhaust quickly.  My experience
is that the 5W-30 is consumed at only about 1/2 the rate that the 5W-20
was.  Watch out what you are buying, both types are still in
circulation.  I just saw both kinds at a service station along I-5
north of Bakersfield last weekend (12/9).


	Craig Johnson			uw-beaver!	\
	John Fluke Mfg. Co., Inc.	decvax!microsof!  \
	Everett, Washington		ucbvax!lbl-csam!    >  fluke!vince
					allegra!	  /
					ssc-vax!	/