Viscosity question

[dgp123]

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Your biggest problem?

Forget talking about oil in "weights"...."weights" is just stupid, wrong labeling for the masses and will never give proper understanding.

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wow, ok, no "biggest problem", sorry for using the weight term inappropriately.

speaking of viscosity in absolute terms makes sense to me. that's why I was confused. I interpreted the numbers "0" and "40" as absolute values for cold and hot temps, which is what confused me because it seemed to defy logic (an oil thickeing at cold temps)

FD777- thanks for the link to the graph! that answers my question

 

[dgp123]

also, if an SAE 30 thickens up to a 30 in the cold, how could that be bad? if a 30 wasn't capable of being distributed through the engine well why would we ever want a 30

 

[G-MAN]

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also, if an SAE 30 thickens up to a 30 in the cold, how could that be bad? if a 30 wasn't capable of being distributed through the engine well why would we ever want a 30

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A SAE 30 doesn't "thicken up" to a 30..."30" is not a measurement of viscosity.

A SAE 30 is an oil that has a vis between 9.3 and 12.49 at 100C. How thick it is at cold temps is irrelevant and isn't measured. As long as it's between 9.3 and 12.5 at 100C, it can be labeled SAE 30.

 

[dgp123]

ohhh ok thanks, the posts in combination with the graph have helped me put it all into perspective.

it's just a tough thing to put into words, both to ask the question and to answer it...

i feel like i've learned a lot tonight!

 

[dgp123]

I like this site because people neither ignore questions or eDestroy people for asking things!

 

[Merkava_4]

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A SAE 30 doesn't "thicken up" to a 30..."30" is not a measurement of viscosity.

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I'm wondering where they get the number 30 from then.

 

[Gary Allan]

Well, it's a "range" of viscosity. I wonder where they got the assigned number too

I'll pull a Ronnie Reagan Iran-Contra here and say "Well, I may have known at one time, but right now I don't recall.".

 

[Merkava_4]

LOL! . . .

 

[Gary Allan]

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ohhh ok thanks, the posts in combination with the graph have helped me put it all into perspective.

it's just a tough thing to put into words, both to ask the question and to answer it...

i feel like i've learned a lot tonight!

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Most people's problem with the concept is that they'll hear "it's like a 10 weight when cold ..and a 30 weight when hot" and keep the vision of how 10w-30 would pour at room temp. They never figure out that 10 weight oil @ -25f is very thick and that 30 weight oil @ 100C is very thin. The assertion is correct ..but, without orientation, is obviously misleading.

 

[G-MAN]

Here's an example of what oil looks like at -40F:

 

[TallPaul]

Study this chart and you will learn a lot.

BTW, I suspect a conventional SAE 30 oil would likely pass the 20w test and so be a 20w30. In fact "30w" is not even defined on the chart.

 

[FD777]

G-MAN, I completely agree. I never liked the explanation: It behaves like this oil at cold and behaves like this oil at hot. Mainly because, an SAE10/20/30/etc. has no definite viscosity at "cold" temps.

If you read the thread (from the link in my previous post), I was going against this explanation of multi-viscosity oils.

Anyways, for this thread, I mis-interpreted some posts... I shoulda stuck to my original assertion. I hope I didn't confuse the OP even more...

 

[AEHaas]

These may help you understand viscosity, the first one is more complete:

http://ferrarichat.com/forum/faq.php?faq=new_faq_item#faq_haas_articles

http://theoildrop.server101.com/forums/s...ge=0#Post258506

aehaas

 

[pp_rp]

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Your biggest problem?

Forget talking about oil in "weights"...."weights" is just stupid, wrong labeling for the masses and will never give proper understanding.

Think in kinematic viscosity. cSt.

An SAE 30 or XW-30 will be around 10.5 cSt@100°C and 60 cSt@40°C and way much thicker like 4000 cP at -25 °C (now this part determines, 5W, 10W, 0W...

BTW 90W gear oil is about the SAME as 50W engine oil.

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This is correct !

 

[AEHaas]

The term "weight" is often mistaken to mean the viscosity of the oil. This is not the case. We should use the term "grade" instead. For example, use a 5W30 grade oil, not to say use a 5W30 weight.

aehaas

 

[Tempest]

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The 0, or lower number, is the base viscosity of the oil before viscosity improvers (VI) are added.

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Not quite true. The base oils are thicker than the winter rating, but have pour point depressants added to them that prevent wax crystal formation, which makes them behave like a thinner oil at lower temps.

G-Man, great vid.

 

[TallPaul]

It would be wonderful if the oil company would provide the 100C viscosity of the oil mix prior to adding VII (base oil and all additives but VII). Then we would know how robust the base oil is. For example, two 10w30s could have base oil additive (except VII) 100C viscosities of perhaps 5.5 and 6.8. It would seem to follow that the latter would have the higher HTHS.

 

[bruce381]

""For example, two 10w30s could have base oil additive (except VII) 100C viscosities of perhaps 5.5 and 6.8. It would seem to follow that the latter would have the higher HTHS.""

Thats correct thicker base oil with LESS VII will have a higher HTHS then a lighter oil with a lot of VII.

Base stock ratios are propritary and not enough interest for any mfg to enclude that

 

[dgp123]

thanks for your input, everyone. it definately makes much more sense looking at it as a "grade" rather than weight. I was checking out some of the charts that some of you posted and just out of curiousity, at what viscosity does an oil usually become too thick to be pumped/be beneficial to the engine? is it 60000 mPa-s as may be indicated in the chart TallPaul linked to or am I reading it wrong.