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From: dennis@vrdxhq.UUCP (R. Dennis Gibbs)
Newsgroups: net.auto.tech
Subject: Re: What motor oil should I use?
Message-ID: <2272@vrdxhq.UUCP>
Date: Wed, 20-Nov-85 09:51:19 EST
Article-I.D.: vrdxhq.2272
Posted: Wed Nov 20 09:51:19 1985
Date-Received: Sat, 23-Nov-85 04:19:36 EST
References: <561@ihwpt.UUCP> <2435@cal-dbb.fluke.UUCP>
Distribution: na
Organization: Verdix Corporation, Chantilly, VA
Lines: 32
Summary: Higher viscosity doesn't really protect better

In article <2435@cal-dbb.fluke.UUCP>, bruce@fluke.UUCP (Bruce Reynolds) writes:
> 
> I have used only 20W-50 oil for the past ten years or so.  According to my
> Toyota owner's manuals, this is good protection down to 10F.  And it sure
> makes me *feel* more comfortable on really hot days in the summer.
> 
> If the tradeoff is thick oil & better protection versus thin oil & better
> gas mileage, I would choose the better protection.  
> 
> So what does everyone think?  Nowadays, 15W-50 is available.  Would that be
> perfect?
> 
> --
> --bruce
> -- 
> Bruce M. Reynolds              {decvax,ihnp4}!uw-beaver!--\
> John Fluke Mfg. Co., Inc.                 {sun,allegra}!---> fluke!bruce
> (206) 356-5421                 {ucbvax,hplabs}!lbl-csam!--/

I don't think the tradeoff you mention is valid anymore.  What's really 
important is how much temperature/pressure a given lubricant can take without
oxidizing excessively.  This is where synthetics excel.  I would hate to
think what's happening in your Toyota's engine when it is 20 degrees F outside
and you have 20W-50 in your crankcase.  It will take considerably longer for
20W-50 oil to begin circulating readily at that temperature than a 5W-30
would.  Since the vast majority of engine wear occurs at startup, you want
to avoid having an oil of high viscosity during low ambient temperatures.

The above only addresses one aspect (engine wear) that a motor oil must
provide.

               Dennis Gibbs