Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.1 6/24/83; site umcp-cs.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!mhuxj!ihnp4!zehntel!hplabs!hao!seismo!umcp-cs!prophet
From: prophet@umcp-cs.UUCP (Dennis Gibbs)
Newsgroups: net.auto
Subject: Multi-Viscosity Oils
Message-ID: <131@umcp-cs.UUCP>
Date: Wed, 26-Sep-84 17:42:54 EDT
Article-I.D.: umcp-cs.131
Posted: Wed Sep 26 17:42:54 1984
Date-Received: Fri, 28-Sep-84 06:47:47 EDT
Distribution: net
Organization: U of Maryland, Computer Science Dept., College Park, MD
Lines: 33


<>

Several people have recently expressed interest in exactly what is a multi-
viscosity oil.  The answer is actually quite simple.

A multi-viscosity oil, such as a 10W-30 oil, means  that  at  zero  degrees
fahrenheit, the oil will have the same thickness as a straight weight  10W.
It also means that at a high temperature  (I  think  the  standard  is  210
degrees) the oil will have the same viscosity as a straight 30  weight.

This does NOT mean that the oil doesn't get thicker as it gets  colder,  it
just means that its viscosity value changes from a 30 weight  at  operating
temperature to a 10W weight at zero degrees fahrenheit.

So, in essence, what is happening is  that  you  are getting the high-temp-
erature protection of a 30 weight, and the low temperature protection of  a
10W weight. Both a straight 10W weight and a straight 30 weight get thicker
when it gets cold, but a 10W weight is always thinner than a 30 weight.

Also, there is a common misconception that the heavier the oil, the  better
the oil protects.  This isn't necessarily true.  What is important  is  how
much temperature and pressure the lubricant can take without oxidizing  ex-
cessively.  This is where Synthetic lubricants excel.

                                     Dennis

-- 
Call-Me:   Dennis Gibbs, Univ. of Md. Comp. Sci. Center.
UUCP:	   {seismo,allegra,brl-bmd}!umcp-cs!prophet
CSNet:	   prophet@umcp-cs
BITNET:    GIBBS@UMDB
ARPA:	   prophet@Maryland