<VV> awl

[N. Joseph Potts]

I thought synthetic liquid lubricant ALSO was made from crude oil. If it
isn't, what IS it made from?

Joe Potts
Miami, Florida USA
1966 Corsa coupe 140hp 4-speed with A/C

-----Original Message-----
From: virtualvairs-bounces at corvair.org
[mailto:virtualvairs-bounces at corvair.org]On Behalf Of Padgett
Sent: Monday, June 27, 2005 5:16 PM
To: virtualvairs at corvair.org
Subject: <VV> awl



>Pag,  Multi-vis oil is NEVER  thick......the top number shows that LAB
>testing shows that it "PROTECTS"  as well as 50 wt  oil that is the same
>temp.

Huh ? My SAE books show measuring viscosity *ranges* at two different
temperatures  - "W" (Winter)  at -18C in centipoises  and in centistokes
at  100C. The lab tests are ASTM D 2602 for W and ASTM D 445 for hot.

Incidentally at 100C,  50 weight has 4-5 times the viscosity (drag) of 30
weight).

In conventional oils this is achieved with a straight weight base and
adding long chain polymers to modify the characteristics. These break down
in time into not-so-long-chain and the oil approaches an intermediate value
straight weight. Before I got deep into 3800 engines (the georotor oil pump
has different characteristics) I used to be able to tell when it was time
to change the oil by a 2-4 psi drop.

Synthetics can be (not saying are) much more stable. I am just starting to
try some of the new blended oils but so far am not particularly impressed.
Of course if crude prices go high enough, synthetics may turn out to be
more economical.

The SAE is celebrating its 100th anniversary this year. My books are not
quite that old.

Padgett