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Old 12-29-2011, 10:46 AM   #1
bulwnkl
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Member#: 41070
Join Date: Aug 2003
Location: Arizona
Vehicle:
2005 Black Tiger
(Black Turbo Baja)

Default This is why your motor oil shears to a 20-grade

http://www.machinerylubrication.com/Read/518/motor-oils

Yes, the article talks about GF-3. Ignore that, and read the first couple sections about the operating principle(s) at work. Take care that you are not too taken in by the subsequent conclusions based upon facts not in evidence, nor be distracted by questions whose answers were given in the sentence before the questions were asked.
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Old 12-29-2011, 12:28 PM   #2
bluesubie
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Default

Quote:
Originally Posted by bulwnkl View Post
... Take care that you are not too taken in by the subsequent conclusions based upon facts not in evidence, nor be distracted by questions whose answers were given in the sentence before the questions were asked.
Well what fun is that?!?!?

Some of my favorite sections:

Quote:
... Antiwear additives are important in the absence of a hydrodynamic film, such as in the valve train. The antiwear additives are activated by frictional heat, which causes them to react with the hot surface and form a chemical barrier to wear...

...Certainly engines that have experienced significant ring and liner wear benefit from thicker oils. Thicker oil use results in compression increases, performance improvements and reduced oil consumption. ...

...Every fluid is a compromise. Oils recommended by the auto manufacturers seem to compromise protection from wear under severe conditions to gain fuel economy and catalyst durability. It is important to recognize that to use a product that offers more protection from wear will most likely compromise your warranty. Thicker oils also compromise cold temperature flow, which may be of concern depending upon climate and season. ...

...The best protection against wear is probably a product that is a little thicker (such as SAE 10W-30 or 15W-40) and has more antiwear additives than the oils that support the warranty. The best oil for your vehicle depends on your driving habits, the age of your engine and the climate you drive in, but it is not necessarily the type of oil specified in the owner’s manual or stamped on the dipstick. ...
And I don't get why wear tests are conducted in such old engines. What relevance does wear in a 1994 Nissan engine have to do with wear in a 2012 305 hp turbocharged STI?
Quote:
The Sequence IVA test fixture is a 1994 Nissan KA24E, 2.4-liter, water-cooled, fuel-injected engine, 4-cylinder in-line, overhead camshaft with 2 intake valves, and 1 exhaust valve per cylinder.
http://www.swri.org/4org/d08/gastest...st/default.htm
http://www.astm.org/Standards/D6891.htm

And I'm not sure that I buy the argument that some people make that if permanent shear is not causing any elevated wear (in a $30 single pass uoa), then no damage is being done or that there is no chance of running into a lubrication related failure. Some people will take comments from a uoa lab as gospel and fall into a false sense of security. You may or may not remember "BuickGN" on bitog that had an engine failure after countless great uoa's.

Quote:
UOAs are a great tool in the Management of any machinery that uses liquid lubricants. Unfortunately, their real value is often misunderstood ... Single pass (random) UOAs will provide some information regarding wear metals but unless you have a history of your engine’s performance up to around 1 million miles the results are simply that – UOA results!
http://www.bobistheoilguy.com/used-oil-analysis/

I think I failed the exercise.


-Dennis

Last edited by bluesubie; 12-29-2011 at 04:16 PM.
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Old 12-30-2011, 11:45 AM   #3
bulwnkl
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Join Date: Aug 2003
Location: Arizona
Vehicle:
2005 Black Tiger
(Black Turbo Baja)

Default

I may have, too.

It is unfortunate that they provide no basis for the conclusions they draw regarding 'best' or 'better' viscosity choices. There is some good info in there, though.
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