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From: fern@polyof.UUCP ( FTG )
Newsgroups: net.auto,net.auto.tech
Subject: Re: questions: Oil, oil coolers, paint shops
Message-ID: <172@polyof.UUCP>
Date: Fri, 22-Nov-85 17:31:41 EST
Article-I.D.: polyof.172
Posted: Fri Nov 22 17:31:41 1985
Date-Received: Thu, 28-Nov-85 03:49:48 EST
References: <653@wjh12.UUCP>
Organization: Polytechnic Inst. of NY, Farmingdale
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Xref: watmath net.auto:8751 net.auto.tech:302

> xxx
> questions about oil:
> who has experience with synthetic oils??
> would they be silly in a big old American V8.I'm especially
> interested in the 'heavy' (15w-50) new Mobil 1.
> 
There seemes to be some confusion regarding "multi-weight" oils
5W-40 for example means that at some low temperature, the viscosity
of the oil falls within some appropriate range, and at some other 
high temp the oil viscosity is still withinh that appropriate range.
This means that at any temp inbetween the upper limit (which is defined by
the big number) and the lower limit (defined by the little number)
that the oil has a viscosity which falls into appropriate limits.
For single grade oils 5 10 20 etc. the viscosity of the oil
at room temp is almost always proportional to the number. For "mulitweight"
oils the viscosity need bear no relation to the numbers, ie 5-30 maybe
on average a higher viscosity oil than 5-40. The only thing that the numbering
scheme ensures is that the viscosity is appropriate in the temp range
defined by single weight numbers.



			FTG

ps, as always dietz etz