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oil viscosity - small part of a very long story... Posted by JimBlake [Email]  (#141)  [Profile/Gallery]
(more from JimBlake) on Wed, 24 Apr 2002 10:25:45
In Reply to: Comments on new Mobil1 formula? and difficult ques., AP, Tue, 23 Apr 2002 18:44:55 Members do not see ads below this line. - Help Keep This Site Online - Signup |
From Obert - "Internal Combustion Engines and Air Pollution" chapter 16...
SAE viscosity no.
the "W" suffix means that the viscosity is measured at 0 degrees F. Otherwise it is measured at 210 F. So a 10W-30 oil meets the viscosity range defined by SAE-10W when it is measured at 0F, and it ALSO meets the range of SAE-30 when it is measured at 210F. So its not really a matter of "converting" one number into the other.
The spec is apparently writtin in terms of Saybolt Universal Seconds, which is not exactly units of viscosity. It can be approximately converted into centistokes...
5W is below 1300 cst at 0F
10W is between 1300 & 2600 cst at 0F
20W is between 2600 & 10,500 cst at 0F
20 is 5.73 to 9.62 cst at 210F (5.59 to 9.36 cst at 212F)
30 is 9.62 to 12.93 cst at 210F (9.36 to 12.58 cst at 212F)
40 is 12.93 to 16.77 cst at 210F (12.58 to 16.26 cst at 212F)
50 is 16.77 to 22.68 cst at 210F (16.26 to 21.94 cst at 212F)
That's the extent of the table in my textbook. Maybe check sae.org for more, but it'll probably cost money to get the whole standard. Its probably like a bunch of books.
Without additives, a petroleum oil which meets SAE-20 when measured at 210F is "probably" going to meet SAE-20W when it is measured at 0F. Everything changes viscosity with temperature; oil, water, maple syrup, even glass. The oil additives make it change LESS with temperature.
Notice that even 5W-50 has 0F viscosity 50 TIMES HIGHER than its 210F viscosity.
You thought it would be simple, didn't you ;-)
posted by 131.184.14...
, Wed, 24 Apr 2002 10:54:20, Wed, 24 Apr 2002 10:25:45 <-- Viewing This Message, Wed, 24 Apr 2002 10:59:04, Wed, 24 Apr 2002 12:52:30
, Tue, 23 Apr 2002 19:32:14, Wed, 24 Apr 2002 09:45:21
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