This quote from Bob has gotten me confused...

[The_Oz]

quote:

---

Originally posted by BOBISTHEOILGUY:
I think this may be the time to come out and explain something here that is being over looked in this issue and GeorgeCLS or Mola can correct me if I miss the point. So here it is,

Newtonian vs Non newtonian fluids.

In the case of a mineral oil, you start out with a base oil of 15wt(15w40 for example). You then add some VII to enhance it to the 40wt as it heats up. This is a non newtonian fluid.

In the case of a real full synth, You take a 40wt base oil synth. In most cases it has the ability to flow in lower temps to what ever it is tested to.So for example, a company like M1 can make a 40wt synth, test it to the flow propertis of a 15wt and label it, take the same oil, retest it to a 10wt property and label it,again use the same oil and test it to a 5wt and 0wt and relabel those, all being the same oil. This is not a bad thing, but in fact is a win win for everyone as it lowers the cost of production to one oil for many viscosities and also, you could have a 15w oil that actually perform down to a 5wt oil in really sub cold temps if needed. But in all, it's still a straight 40wt with no VII added, therefore it has a natural ability to resist the cold flowing properties.

This is a netownian fluid or actually a straight wt oil with the flow properties of some non netonian fluids. Now there is some so called full synth's that need some assistance to get a further spread on the numbers and there is some help added there but in the case of full synths this is the basic premise. Mobil stands out as being one of those from my understanding. Castrol on the other hand would not be.

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I wanted to start a new thread regarding this statement since I think it would be off-topic to talk about it in the Turbocharger failure thread.

Anyway, I am a tad confused about how oil companies come up with the viscosity rating that we see on the labels. I think it was MolaKule or someone who told me that ALL multi-vis oils always starts at the high number as the base (ie. 30 weight in a 10W30 rated oil), and then made to flow like a thinner oil at startup (ie. 10W in a 10W30 rated oil).

Instead, Bob - with his statement above - says that on some oils this maybe true, but others (such as dino oil) start at the low number specified (ie. it is a 10 weight oil in a 10W30 rated oil), then made to thicken out.

Can you guys clear this up for me, once and for all

Thanks,

Oz

 

[MolaKule]

TooSlick,

"A very wide range oil, like a 0w-40 or 5w-50 is going to tend to have a higher viscosity index. However, these grades tend to be less stable over time and have higher evaporation rates. When you start out with a low molecular basestock and add a significant percentage of VI modifier, this is what tends to happen."

A lot depends on the basestock's original VI. For high quality true synth bases (Group IV, V), the original VI will be so high that you may not need VII's. In synthetic blending, you might blend a 4.o cSt PAO with a VII of 210 (25%), an 8.0 cSt PAO (say 25%) with a VI of 160, a 30 cSt Pao (say 45%) with a VI of 135, and a 2.0 cSt ester (5%) with a VI of 225, and pour in your additives. Considering the small thickening effect of additives, and you would have a VII of 185, and a multigrade oil of say SAE 5W40. Since each of the base fluids already have an inherently high VI, little or no VII needs to be added. If the base oil is temperature stable (high oxidation resistance) then you have have less volatility (tendency for oil and additives to evaporate).

In most dino's, you start out with a low molecular basestock and add VII's to span the temperature range of operation. In blends, the addition of small amounts of PAO's and esters help the base stock's stability and increase the VI without the addition of high concentration of VII's.

[ September 10, 2002, 03:18 PM: Message edited by: MolaKule ]

 

[satterfi]

Bob’s definition of Newtonian and non-newtonian is confusing to me. I haven’t heard that viscosity vs temperature is part of the definition.

I thought newtonian fluids had a linear stress versus rate of strain curve while non-newtonian fluids didn’t.

For example, with newtonian fluids in a plain bearing at 1000 rpm you had 1hp lost due to viscosity loses. At 5,000 rpm you would have 5hp lost and at 10,000 rpm you would have 10hp lost.

For non-newtonian fluid the hp loses at 1k, 5k and 10k rpm might be 1hp,6hp,15hp respectively.

 

[BOBISTHEOILGUY]

Most homogeneous liquid lubricants are Newtonian fluids. Notable exceptions are multiviscosity grade lubricants that contains special polymeric additives. Fluids that have different viscosities for different shear rates are called non newtonian fluids.

A straight wt oil is a newtonian fluid. No special polymeric or VI improver additives used.

 

[The_Oz]

quote:

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Originally posted by BOBISTHEOILGUY:
Most homogeneous liquid lubricants are Newtonian fluids. Notable exceptions are multiviscosity grade lubricants that contains special polymeric additives. Fluids that have different viscosities for different shear rates are called non newtonian fluids.

A straight wt oil is a newtonian fluid. No special polymeric or VI improver additives used.

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Bob, Lamens terms please

From what I gather from you though is this: Let's take for example Castrol GTX 10W30. IF it is non-newtonian, then it is a 10 weight oil as a base, formulated to thicken to a 30 weight at 100C. Now, correct me if I'm wrong, but with this type of method, wouldn't the oil rapidly decrease its viscosity to 20 weight since - I believe - the VII are working overtime to let the oil flow as a 30 weight....rather than the other way around?

Regards,

Oz

 

[Johnny]

OZ: Here it is in simple form. Now I am refering to dino oil only, not synthetics (at least not Group IV synthetics)

I don't care which brand you pick, Pennzoil, Chevron, Mobil, Castrol, Valvoline, any of them.

A 5W30 starts out as a 5 weight oil. A 10W30 starts out as a 10 weight oil. They add VI improvers to the oil to make it perform like a 30 weight at higher temps.

That't it.

 

[Patman]

Johnny, are you sure about that? I used to think that too, but now I understand that the first number is not a viscosity at all, but just an arbitrary number given that indicates how it performs on a cold crank test. One 5w30 from one brand may start out as a 20wt oil with a slight bit of VI, while another could start out as a 10 or 15wt and have more VII. And with a synthetic, it could actually be a straight 30wt (or close to it) and need little or no VI, but instead just has the ability to flow well enough at low temps to qualify with a 5 rating to get the 5w30 designation.

 

[Jay]

I think what's confusing you , Oz, is Bob is using "w" in the first term of the viscosity rating as "weight" when it's actually "winter". Patman is correct; the fist term in an SAE multiviscosity oil rating is not a viscosity rating but a cold temperature pumpability and flowability rating that has no direct relationship to weight number on the right.

Since oil changes viscosity with temp it makes sense to rate it's viscosity at a fixed temp. That fixed temp is 100 deg C and the number on the right is the weight of the oil.

 

[Jay]

My understanding is this:

The cold temperature or "w"designation is assigned to a motor oil according to the outcome of two cold temperature tests--the cold crank simulator (ASTM D-5293) and the mini-rotary viscometer (ASTM D-4684). If an oil, any weight oil, can fall under the maximum allowable cP for the two tests it earns that "w" classification. If, for example, a 40 weight oil scored a cP rating under half of the allowable maximums for the two 5W tests, then the oil manufacturer can try for the 0W designation. The temperature of the oil is chilled another 5 deg C and the two tests are run again.

The reason I say that the first number in a multiviscosity rating bears no relationship to the second is that there's no such thing as a 0 weight, 15 weight or 25 weight motor oil. SAE weights start at 5 and go 5,10,20,30,40,50. But there is a 0w, 15w, and 25w cold temperature designation. Also the cold temperature designation uses different units than the SAE weight-- cP vs cSt.

I've read through your post a couple of times, Bob, but it seems to me that there are many ways to make a certain multiweight oil regardless of the basestocks. An oil maker could start with 20 weight basestocks, add VI improvers to make his oil perform as a 30 weight, then add enough pour-point depressants to get the "w" rating he's shooting for.

 

[MolaKule]

Jay,

Just to add to the confusion, some VII additives also serve as pour-point depressants, anti-oxidants, and friction reducers.

 

[BOBISTHEOILGUY]

well If they weren't confused before, they probably are now.

I was trying to cover the basic point on the confusion, but the additional points are greatly appreciated.

 

[BOBISTHEOILGUY]

Let me try this again....

lets take dino oils....

First you start with a base weight oil of say 10wt and the flow properties are that of a 10wt oil based on the cold cranking simulator tests (explaination of this test at the bottom). Now add VI improvers to increase or expand to the 10weight oil the flow chareteristics of a 30 weight, so now it flows like a 30wt oil when up to the 100degC.

All right, recap, 10wt oil flows like a 30wt when temp=100deg C.

All dino multi visocisy oils are considered a non newtonian fluid.

Now take a base weight oil of say 30wt., This is a straight 30wt oil with no VI improvers added. It flows as a 30wt at 100degC and of course it is still a 30 weight oil when cold.

This is considered a newtonian fluid.

Now, lets forget about newtonian/non newtonian definitions for a minute.

The way I understand a full synth oil works is like this...

Start with a base oil of 30 weight. With the natural flow properties of full synth's, you can measure using the cold cranking simulator for example, to say what a 10weight oil would flow. If the oil will provide the same basic cP(centipoise)reading of what a 10 weight oil, then it can be classified as a 10w30, even though it doesn't use any VI improvers in this formula.

Take this same oil, 30weight, re run the same CCS test, and now test the flow to what a 5 weight oil does, if it meets that spec, it now can be labeled as a 5w30 even though it is being used as a 10 weight in the previous example. Again, with no VI improvers. And the same to say a 0 weight oil, again now labeled as a 0w30.

Recap, a full synth, you start out with the higher # base oil and measure to the lower flow properties, where on dino's, you take the lower #, add VII's and measure to the higher flow properties.

Now, you'll find this is why people say that synth's don't use much if any VII's unlike the same Viscosity dino oils.

It's a little more complex than that but thats' the general priciple on how a full synth works.

Now in some cases, some full synth's may require some addition of VII's to establish the complete spread but not like a dino would.

Now in the case of a blend, You'll find that you take a dino, add say the PAO to get the natural VIIs to establish the spread between the bottom and top #'s. This makes the blend/dino a more shear stable oil because it is using the PAO natural VI to improve the spread(like in a full synth) and not so much the VI improver additive.

code:

---

To measure the starting viscosity of an oil, ASTM

test method D5293 is used. In this test, a steel

cylinder, or 'rotor', is inserted into a

relatively close-fitting copper cup, or 'stator',

filled with the oil in question.



The oil is cooled to a specific temperature at

which point a certain amount of engery is applied

to the rotor to turn it against the resistance of

the oil. The rotor speed is measured to determine

the engine oil viscosity at the chose

temperature. The unit of measurement for

reporting starting viscosity is centipoise(cP).



SAE has set specifications for starting viscosity

associated with the 'W' grade of an oil as

follows:





Viscosity Grade Maximum Starting Viscosity

25W 6000 cP at - 5*C (+23*F)

20W 4500 cP at -10*C (+14*F)

15W 3500 cP at -15*C (+5*F)

10W 3500 cP at -20*C (-4*F)

5W 3500 cP at -25*C (-13*F)

0W 3250 cP at -30*C (-22*F)

( note the '*' denotes the degree mark for

temperature)

---

[ September 07, 2002, 12:22 PM: Message edited by: BOBISTHEOILGUY ]

 

[The_Oz]

Thanks for the explanation guys...I'm not confused....yet

However, my question in my second post is still unanswered: If dino oils start at the low number (ie. 5W, 10W, etc.), then wouldn't it be less stable, shear down very quickly, and rely too much on VII? Also, would it be safe to say that a 10W30 dino oil is "thicker" than 5W30 even at 100C (all else being equal)?

And Bob, do you believe the synthetic blend will be more shear stable than a 100% PAO base?

Thanks,

Oz

 

[VaderSS]

Hmmm, all petroleum based oils start as the xW. Isn't this also true all oils period? It's just that each class of oil requires less of the VI improver to perform as the Wx. All base oils thin with heat, some thin less.

Conjecture;

code:

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VI Improver to Achieve 10W30 Grade

Group I 10%

Group II 5%

Group II+ 3%

Group III 1%

Group IV 0%

---

 

[MolaKule]

"A lot depends on the basestock's original VI. For high quality true synth bases (Group IV, V), the original VI will be so high that you may not need VII's. In synthetic blending, you might blend a 4.o cSt PAO with a VII of 210 (25%), an 8.0 cSt PAO (say 25%) with a VI of 160, a 30 cSt Pao (say 45%) with a VI of 135, and a 2.0 cSt ester (5%) with a VI of 225, and pour in your additives. Considering the small thickening effect of additives, and you would have a VII of 185,
and a multigrade oil of say SAE 5W40. Since each of the base fluids already have an inherently high VI, little or no VII needs to be added. If the base oil is temperature stable (high oxidation resistance) then you have have less volatility (tendency for oil and additives to evaporate).

In most dino's, you start out with a low molecular basestock and add VII's to span the temperature range of operation. In blends, the addition of small amounts of PAO's and esters help the base stock's stability and increase the VI without the addition of high concentration of VII's."

Oz,

You can believe what you want but the above is industry practice.

 

[dragboat]

Molakule,I agree but it raises a question about Dino oils. If you have two 10/30 oils,one a group I the other a group II how does a guy tell which one uses less VII's by the data sheet?
In particuler the Pennzoil and the Mobil 10/30's ?
Can this be done?
The Pennzoil sites data is incorrect in some ways though,the 10/30 shows to have a CP of 3300@-25 when it actually is 7000@-30 I recently found

If you need additional info I will dig it up for you,just to hazard guess would be fine between these two oils if you are willing

Actually it would be a guess as the Mobil data sheet shows the 10/30 to be 10.4 @ 100C when the sample tested at 12.2 @ 100c ?

[ September 10, 2002, 07:42 PM: Message edited by: dragboat ]

 

[MolaKule]

Dragboat, Oz,

OK, maybe I missed the point. And if so please accept my apologies.

If you can find the MSDS sheets and post them on the oil in question, we will give our best effort to determine what base oils it might contain.

There is no way to determine (other than an NMR or detailed GC study) if the oil company or blender started out with say an SAE 10 weight Group I and blended a Group II+ 30 weight into it for a multigrade 10W30 weight. That is a possibility but unlikely. The usual or standard practice for OTC dino oils is to start with the lower viscosity oil, which could be a mix of any of the Groups such as Group I,II, or III of 10 weight and add the VII's to achieve a 10W30 multigrade. First, it is cheaper to simply add VII's to light cut (cheaper still) of oil than to try and blend in bright stocks (the heavier cuts), since bright stocks are more expensive. Bright stocks are usually reserved for gear oils and heavy industrial fluids because they bring a higher price.

Now with synthetics, as I stated earlier you can mix various fluids of various VII's to obtain the VI and SAE weight grade you need with little or no VII additives. My educated guess (from reading the tech papers) is that NEO, Redline, Oil for Life, and Mobil do the above. I also think that Amsoil most likely sticks with a "middle range" PAO of wide viscosity and adds esters for additive compatibilty, friction reduction, and high temp stability.

Is that close to what you guys had in mind?

 

[BOBISTHEOILGUY]

Open'd a bucket of worms didn't I?..

 

[dragboat]

Molakule,"
""There is no way to determine (other than an NMR or detailed GC study) if the oil company or blender started out with say an SAE 10 weight Group I and blended a Group II+ 30 weight into it for a multigrade 10W30 weight. That is a possibility but unlikely. The usual or standard practice for OTC dino oils is to start with the lower viscosity oil, which could be a mix of any of the Groups such as Group I,II, or III of 10 weight and add the VII's to achieve a 10W30 multigrade. First, it is cheaper to simply add VII's to light cut (cheaper still) of oil than to try and blend in bright stocks (the heavier cuts), since bright stocks are more expensive. Bright stocks are usually reserved for gear oils and heavy industrial fluids because they bring a higher price""

No misunderstandings,you answered my questions on the dino oil,and I thank you.Am right with you on the Synthetics,,Thanks again,
dragboat

Bob,some of this stuff comes easy to learn,some,,well without Mola,you and some others it is like being a stranger in a strange land! Can't read or write the languge kinda sorta,,thanks for the site!

[ September 11, 2002, 10:14 AM: Message edited by: dragboat ]

 

[BOBISTHEOILGUY]

Dragboat,

It goes both ways, as myself and many others do learn from others like yourself in many other areas especially when it comes to some of the mechanical priciples involved in an engine and such.

I'm want to say I'm really appreciative of all the contributions and expertise that has been provided here from everyone and this is what has made this board what it is.

bob