Please Explain Viscosity in Simple Terms

[OVERKILL]

The SAE J300 max specified Pumpability Viscosity at 60,000 cP is huge compared to the Cold Cranking Viscosity max viscosity. But one has to ask if the dynamic viscosity measured is a function of the machine(s) used to make the measurements. In other words, is 7,000 cP measured at -25C in a CCS machine really going to measure at the same 7,000 cP at -25C in an MRV machine? The resulting dynamic viscosity measurement could be test machine dependent to some degree.

As Overkill pointed out, pretty much every time the CCS Viscosity spec will end up defining the W Grade that the oil falls in to. If the engine starts, the oil better be "pumpable" ... so seems CCS becomes the limitiing factor because of this reason. As mentioned above, the W grades are more narrow then they seem to appear because it's the narrow band of only a 5 deg C difference in oil temperature that becomes the main defining parameter of what W grade the oil falls in to.

Well, if we look at straight-up PAO base oils, we can see this data because Mobil is generally very generous with what they give us:

So, we have THREE different viscosity measurements for this 8cSt (SAE 20) base oil at -40C:
- Kinematic: 19,000cSt
- Brookfield: 17,590cP
- MRV: 16,200cP

CCS visc is only presented at 5W-xx (-30C) because it clearly doesn't meet the threshold for 0W-xx. You have to step down to SpectraSyn 5 or SpectraSyn Plus 6 for Mobil to provide CCS at -35C:

 

[ZeeOSix]

Yup, that's why I called it a grade there, but I do think it makes it easier to think of it as a "rating" for folks struggling with the concepts.

To add (and not a dig on anyone here) ... I think lots of people struggle with concepts in these discussions because too many non-official terms are used in explanations which can ad more confusion than not. IMO, the best learning is done when people learn to understand and use the right terminology, especially in technical discussions.

 

[Exhaustgases]

I allways explain it in a simple way like this:

- Engine oil is like butter. Stiff when cold, but thin when hot.
- At the 10w-40 printed on the Jug, the left one with the W (..inter) denotes how thick the oil is when it´s cold, the right one denotes how thin the oil becomes when it´s hot, the enigne is running.
- The 10W- and the 40 are meassured the same way, but the meassuring system is different like Fahrenheit and Celsius.
You can not compare it 1:1.

The last one is the most important for understanding, in my Opnion.

I agree with you, though the how thin it is when hot, is equivalent to how thin a 40 weight oil would be at the same temperature.

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And like oh wow! All those charts make this all as clear as mud.
That are posted one post above this post.

 

[ChristianReske]

You have the charts ready with you when you try to explain what "10w-40" printed on a oil bottle means to average Joe in your car parts store?
And average Joe actually would like to read all theses charts that need to be explained and he can understand the charts?
Good luck.
Sometimes a simple and non scientific explanation, even if it is slightly wrong, fits the bill "Teaching People in a simple way, easy and fast" perfect.

It´s a difference between a thread in a oil Forum where you can explain it in lenght and with diagramms, links etc. and where questions can be asked and get answerd by experts, and when you simply talk with a customer in a car parts store.

Am i am the only one wich notice the difference between explaining things in deepth, correct in a Forum vs. talking to a fellow customer in a Store?

So, next time when a customer in a car parts store ask "What does 10w-40 mean?" i crab the whiteboard form my car, the charts, the SAE J300 table and explain it to him for 20 Minutes just to be scientific correct?

Ohkay. Sure.

 

[ZeeOSix]

So, next time when a customer in a car parts store ask "What does 10w-40 mean?" i crab the whiteboard form my car, the charts, the SAE J300 table and explain it to him for 20 Minutes just to be scientific correct?

The simplest I could come up with is: The first number (xW) is the cold (Winter) thickness rating (grade) - the lower the number the thinner and better flowing it is when cold. The 2nd number is the rating (grade) of how relatively thin or thick the oil is when hot (212F) in a running engine - the larger the number, the thicker the oil when hot. And make the comment that they are two separate and unrelated numbers for two separate reasons - a separate cold and hot thickness rating/grade, and that oil always gets thinner as it gets hotter. That's as simple as it gets.

Then I'd just say "Don't worry about it, what oil grade does the owner's manual say to use?". Then I'd write this on a piece of paper and say you can learn more about it here with some cool charts, graphs and tables: bobistheoilguy.com/forums

 

[ChristianReske]

Yes, that is also my way to explain it, but sometimes people are still puzzled, because... "If the oil is thicker when it´s cold and thinner when hot, why it is not labeld 40w-10"? And that´s a good question wich actually shows how stupid this system is in real life, for the average joe customer.
But yeah, the engineers at the universitiy knows best...

Thats why i came up with my simple and unsientific explanation of "they are like Fahrenheit and celsius" One simple sentence and people are "Now i get it!" Whats wrong about to explain things to customers in a store in one simpel sentence, even when it is wrong?

 

[ZeeOSix]

Yes, that is also my way to explain it, but sometimes people are still puzzled, because... "If the oil is thicker when it´s cold and thinner when hot, why it is not labeld 40w-10"? And that´s a good question wich actually shows how stupid this system is in real life, for the average joe customer.
But yeah, the engineers at the universitiy knows best...

In simple terms, SAE came up with a separate grade (rating) scale for W grades and for KV100 grades. They are not related in any way, so saying 40W-10 makes no more sense (actually less sense) than saying 10W-40.

The W grades go from 0W to 25W, where 0 is the thinnest represented by the smallest number. The KV100 grade goes from 8 to 60, where 8 is the thinnest and again represented by the smallest number. So each independant grade scale goes from a small number for the thinnest grade to the larger numbers for thicker grades. That makes sense to me.

Again, the first most important thing to understand is that the W grades and KV100 grades are totally separate grade scales and not connected in any way.

 

[KrisZ]

Am i am the only one wich notice the difference between explaining things in deepth, correct in a Forum vs. talking to a fellow customer in a Store?

So, next time when a customer in a car parts store ask "What does 10w-40 mean?" i crab the whiteboard form my car, the charts, the SAE J300 table and explain it to him for 20 Minutes just to be scientific correct?

Ohkay. Sure.

Never had that happen. Sounds like you are hanging around the automotive section just to give unsolicited advice to your “fellow” customers.

Perhaps that explains your insistence on simple, yet wrong analogies. Makes you look and feel like you know more to your peers, without actually knowing. Keep hanging around oil isles and “educating” your “fellow” customers. I’m sure they appreciate the “education”.

 

[ChristianReske]

Yep, now you are definetly rude and insulting.

 

[KrisZ]

Yep, now you are definetly rude and insulting.

Rude, probably, but insulting?

What’s insulting is you knowingly misleading people with your feel good analogies and feeling like you’re doing them a favor. It would’ve been a bit better if you were ignorant as well, but you admitted you know these are not correct.

 

[kschachn]

In simple terms, SAE came up with a separate grade (rating) scale for W grades and for KV100 grades. They are not related in any way, so saying 40W-10 makes no more sense (actually less sense) than saying 10W-40.

The W grades go from 0W to 25W, where 0 is the thinnest represented by the smallest number. The KV100 grade goes from 8 to 60, where 8 is the thinnest and again represented by the smallest number. So each independant grade scale goes from a small number for the thinnest grade to the larger numbers for thicker grades. That makes sense to me.

Again, the first most important thing to understand is that the W grades and KV100 grades are totally separate grade scales and not connected in any way.

In some ways it might have been better if numbers were not used for the winter rating. That way it might reduce confusion. Something like A-40 or B-40, but then people would think it means quality of the oil or something. No matter what is used there will probably be misunderstanding.

 

[SuperSalad]

In some ways it might have been better if numbers were not used for the winter rating. That way it might reduce confusion. Something like A-40 or B-40, but then people would think it means quality of the oil or something. No matter what is used there will probably be misunderstanding.

Cool-40
Chilly-40,
Cold-40
Frigid-40
Forgetthisletsmovesouth-40

 

[OVERKILL]

I agree with you, though the how thin it is when hot, is equivalent to how thin a 40 weight oil would be at the same temperature.

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And like oh wow! All those charts make this all as clear as mud.
That are posted one post above this post.

It's quite simply once you understand it. My suggestion is to keep going over the material until you do. You can't explain something unless you properly understand it yourself.

 

[ChristianReske]

My suggestion is to keep going over the material until you do.

And this simply takes time.

When a Buddy is there and would ask, i simply would take the wounderfull Book about engine oil from Mr. Mitchell (German Translation) from my bookshelf and we could talk about it while whe have a Coffee or Beer.

When you dont have time or Books around, then... what?

 

[KrisZ]

When you dont have time or Books around, then... what?

Find another topic? Weather, sports, did I mention weather? Plenty of discussion

 

[ZeeOSix]

In some ways it might have been better if numbers were not used for the winter rating. That way it might reduce confusion. Something like A-40 or B-40, but then people would think it means quality of the oil or something. No matter what is used there will probably be misunderstanding.

Yep, as long as someone doesn't realize there are two separate and unrelated ratings/grades (one for cold starting and one for hot running), then it will always be confusing and misunderstood.

 

[CR94]

Yes, that is also my way to explain it, but sometimes people are still puzzled, because... "If the oil is thicker when it´s cold and thinner when hot, why it is not labeld 40w-10"? ...

Because, contrary to typical assumptions, those numbers are not measurements of viscosity at low and high temperatures, but simply names of viscosity categories (=grades). Words instead of numbers might seem less confusing.

 

[ZeeOSix]

Words instead of numbers might seem less confusing.

See post #92.

 

[Exhaustgases]

It's quite simply once you understand it. My suggestion is to keep going over the material until you do. You can't explain something unless you properly understand it yourself.

I understand fully.

And I explained perfectly, I've noticed people just can't read what I say.

 

[OVERKILL]

I understand fully.

And I explained perfectly, I've noticed people just can't read what I say.

With all due respect, this statement:

Never said they represent the same thing. It is the same oil, the base oil is the low number, the viscosity modified number is the high number.
That is at the operating temperature it "behaves" like oil that has that viscosity number, ie the right hand number. No misconception at all.

Is not correct, and doesn't illustrate that you "understand it fully".