Toyota TGMO 0W-20 SN VOA with VI, TBN, and TAN

[Shannow]

Been pondering that, gut feel is that the HTHS is the relevant one at both the entrance and under the wedge.

The temperature of the "working" oil in the bearing is a mix of what's already been in the bearing and what's refreshed, so it's likely a lot more than 100 as an aside.

Take a 2" journal, 0.0015" radial clearance, and 6,500RPM, and assume that the journal is really pushed hard on the loaded side, and away from the feed hole.

The shear rate adjacent to the feed hole is 750,000, 75% of the 1,000,000 that HTHS is measured at.

There's a pretty good chance that what CATERHAM is measuring is either close to, or in the second Newtonian (High Shear) environment, much closer than the KV.

Provided the engines doesn't have (and it's unlikely to have) too many squirters, the High Shear behaviour is probably the dominant.

 

[CATERHAM]

Originally Posted By: Shannow

Note, while I agree with CATERHAM's Oil Pressure/HTHS assertion for the architecture being tested (squirters, chain oilers, etc. all skew the balance...I disagree vehemently with his assertion that oil pressure equals protection.

A strawman argument, as I have never said "oil pressure equals protection".
What I do assert is that oil pressure is a proxy for operational viscosity and therefore the higher the oil pressure reading on an OP gauge the higher the operational viscosity of the oil in an engine. That's it, end of story.

Now how high an operational viscosity is required for an engine and under what conditions is an entirely separate subject. But knowing what you're operational viscosity is, is a good starting point in the discussion of what viscosity, minimum and maximum is required. In many performance oriented engines that info is provided for you by the manufacturer or tuner; i.e., maintain a certain minimum OP at a specific elevated engine rpm.

 

[Garak]

Originally Posted By: CATERHAM
What I do assert is that oil pressure is a proxy for operational viscosity and therefore the higher the oil pressure reading on an OP gauge the higher the operational viscosity of the oil in an engine. That's it, end of story.

Now, the big question is how much operational viscosity equates with protection.

 

[CATERHAM]

If you don't know specifically as I mentioned then a good place to start is with the OP test spec's. These conservative figures don't correlate with the minimum operational viscosity that's safely possible if very high oil Temp's are encountered but if you maintain them when and if you do encounter high oil Temp's you are playing it pretty safe with no other more precise OP figures to rely upon.

 

[Garak]

What always concerns me, though, is how much of a safety margin these numbers we see in certain shop manuals really are. If they provide a couple points along the way, that increases the confidence level. But, occasionally we see something like just an idle specification.

 

[Blue_Angel]

Originally Posted By: Shannow
The temperature of the "working" oil in the bearing is a mix of what's already been in the bearing and what's refreshed, so it's likely a lot more than 100 as an aside.


It's interesting to see the graphs in the Ricardo article you linked to. They clearly show the relationship between supply and exit temperature at the bearing and how the delta T changes based on supply temperature, indicating the reduced shear load on the oil at higher supply temperatures.

Originally Posted By: Shannow
Take a 2" journal, 0.0015" radial clearance, and 6,500RPM, and assume that the journal is really pushed hard on the loaded side, and away from the feed hole.

The shear rate adjacent to the feed hole is 750,000, 75% of the 1,000,000 that HTHS is measured at.

There's a pretty good chance that what CATERHAM is measuring is either close to, or in the second Newtonian (High Shear) environment, much closer than the KV.


The Savant Lab article you linked to shows an interesting (to me anyway) bit of information. HTHSV spec is measured at 1 million, but the graphs for the oils tested show that viscosity is dropping rapidly until about that point. Between 0.5 and 1.5 million the falling viscosity levels out and stays fairly stable from there on out to much higher shear rates.

QUESTION: Are all VIIs created equal in that they will transition an oil into the second Newtonian phase at about the same shear rate, or is it possible that certain VIIs could allow an oil to continue to lose viscosity well after that point? IF an oil's VIIs allow it to continue shearing to lower viscosities well after 1 million AND that article is correct in that engine bearing shear rates reach and exceed 5.3 million, those oils could have operational viscosities MUCH lower than what we think, no?

Or am I completely wrong and the high shear 2nd N phase of the oil's behavior is simply an extension of the base oil's high shear VI curve (ie how it would behave without VIIs), giving us some confidence in how thin it will become even at extremely high shear rates beyond where HTHSV is tested?

It would seem to me that the HTHSV spec is only a single data point on a curve, and without knowing what that curve looks like it really doesn't tell us much.

 

[Shannow]

Wow, heaps of great questions, and I don't know...have been questioning a "High Shear" viscosity index for a while, and how it correlates to the regular...haven't found much as yet, still looking.

Logic tells me that the different, better VIIS should have different transitions to the second Newtonian, but again am scratching.

Newtonian is supposed to have the same viscosity at any shear rate, and the second Newtonian is supposed to be the same viscosity at all rates after the temporary shear is initiated. I don't think that it get any lower after that...certainly not in the Savant stuff.

Fig 1 shows shear rates in bearings and oil galleries

So I don't think (again think) that we need to worry greatly past what the Savant papers show.

Am still looking 'though.

 

[CATERHAM]

Originally Posted By: Garak
What always concerns me, though, is how much of a safety margin these numbers we see in certain shop manuals really are. If they provide a couple points along the way, that increases the confidence level. But, occasionally we see something like just an idle specification.

Well in my experience I've never not been able to find the relavent OP spec' at elevated rev's for any engine I've looked into.
But the important thing about becoming familiar with the oil pressure characteristics (and secondarily the oil temp's) of your engine is that you'll learn what the operational viscosity
is at all oil temp's that you'll encounter.
You'll also learn just how high the oil temp's you need before the oil pump is out of by-pass at elevated rev's. And you'll also learn how far above the test spec' your OP will be on fresh oil of the lightest oil grade specified.
And if you're running a premium oil you'll also learn that the OP doesn't drop much over an OCI due to sheer and fuel dilution.
And with time you'll realize that your OP is so comfortably higher than the test spec' even when the oil is as hot as it ever gets that running anything heavier, really is totally counter-productive.

And finally once you're totally addicted to observing your OP gauge you'll start to entertain thoughts of actually running a grade lighter than specified to more closely optimize your operational viscosity. The final stage of true enlightenment for the dyed in the wool oil nerd.

 

[Garak]

Originally Posted By: CATERHAM
Well in my experience I've never not been able to find the relavent OP spec' at elevated rev's for any engine I've looked into.

I'll have to hunt through my books and see what I find. I do remember coming across one alarmingly rudimentary entry somewhere. It very well could be the F-150, but in that respect, there's more than enough literature out there if I wanted the figure. In any case, it escapes me as to what it was for sure.

An OP gauge in the F-150 could be a possibility down the road. The G would be, too, if someone made proper gauge pods for the stupid thing. I wish I had an oil pressure gauge to watch (with alarm) as the oil slowly diluted with fuel from that messed up carb.

 

[Capa]

Originally Posted By: CATERHAM


And finally once you're totally addicted to observing your OP gauge you'll start to entertain thoughts of actually running a grade lighter than specified to more closely optimize your operational viscosity. The final stage of true enlightenment for the dyed in the wool oil nerd.


Lol. By the way, Caterham, I am absolutely loving the 4 quarts of Toyota 0W-20 and 1 quart of Mobil 0W-40 in my Lexus GS400. I'm not one for acoustics but the MPG has seen a slight increase and I couldn't be happier.

 

[dieselbass]

Lots of good stuff. Does all of this contribute in some way to the valve train specifically the lifters, or is this all additive package and a separate conversation?

 

[Blue_Angel]

Did a little digging and found a few more papers at the Savant Labs website.

High Shear behavior of Low Viscosity engine Oils from 80-150C:

http://www.savantlab.com/images/TBS_Pape...iscosity....pdf

This paper has an interesting conclusion that the existing (and old) MacCoull Walther Wright (MWW) equation CAN be used to predict high shear rates beyond gathered data points just as it has been used for predicting low shear rate capillary viscometry.


The Expanding Dimensions of High Shear Rate Viscometry:

http://www.savantlab.com/images/TBS_Paper_-_SAE_2008-01-1621_The_Expanding_Dimensions....pdf

This one looks very interesting, with lots of discussion around VIIs and also the effects of high shear rate at temperatures as low as 40C.


Very High Shear Rate Viscometry:

http://www.savantlab.com/images/TBS_Paper_-_ITC_95_-_Very_High_Shear_Rate_Viscometry.pdf

This one shows an oil tested that loses 15% of its viscosity between 1 million and 6 million and their claim is that it has not yet entered the 2nd Neutonian phase yet.

I have yet to read through all three papers in detail, but I will as soon as I have time. I think a few of my questions may be answered within.

 

[Jasonenginetech]

Originally Posted By: Capa
Originally Posted By: CATERHAM


And finally once you're totally addicted to observing your OP gauge you'll start to entertain thoughts of actually running a grade lighter than specified to more closely optimize your operational viscosity. The final stage of true enlightenment for the dyed in the wool oil nerd.


Lol. By the way, Caterham, I am absolutely loving the 4 quarts of Toyota 0W-20 and 1 quart of Mobil 0W-40 in my Lexus GS400. I'm not one for acoustics but the MPG has seen a slight increase and I couldn't be happier.


Kind of off topic - I'm interested in the Caterham blend idea. My question is: Do the different additive packages of the two oils clash?

I would like to run three quarts of Mobil 0w-20 and 1.4 quarts of Mobil 0w-40 in my Fiesta ST. Just concerned about the different additive packages.

 

[147_Grain]

Mobil's additives in their 0W-20 and 0W-40 weights won't clash and you'd end-up with a 5W-30 that is a about 8% to 10% thicker at high temps with a lighter viscosity at start-up.

 

[dailydriver]

I am more concerned about 'clash' between the diverse add packs and base stocks of the 4 quarts of Red Line 0W-40, and the 2 quarts of one of the 0W-20s I want to thin it out with (TGMO, MGMO, or Sustina). But not really.

 

[Capa]

I previously was running 4 quarts of Mobil 0W-20 and 1 quart of Mobil 0W-40. I ran the oil for a year on a vehicle that is about 16 years old. You don't need to worry about these oils clashing.

 

[Clevy]

Tgmo is a Mobil product. So I doubt they are gonna clash.
And that API stamp on the front means it can be mixed with any other API stamped oil.
So mix away

 

[Gokhan]

I had them run an FTIR (Fourier-transform infrared spectroscopy) on the same virgin-oil sample so that I could get a baseline for the sulfation, nitration, and oxidation values, which directly correlate with the TAN and oil life. Of course, virgin oil has no sulfation, nitration, and oxidation but the numbers that are calculated by a self-consistent algorithm are to be subtracted as a baseline from future UOA samples. Therefore, this is for information purposes as a baseline for future samples. For this VOA sample, you would simply subtract these numbers from themselves, resulting in a zero (0) for each value.

TGMO 0W-20 SN WearCheck Laboratories baseline values for virgin oil:

Sulfation: 58%
Nitration: 33%
Oxidation: 68%

"FTIRs work by an auto-reference algorithm and the results are strictly an estimate of what the FTIR program calculates for the values. With the older FTIRs, you had to have a baseline of the actual product and process the used oil sample against it to establish true values. This is typically not done by used oil analysis production laboratories as it would require a baseline reading of each individual new oil product requiring the lab to know what the exact product was before processing. Very impractical, and clients often do not report the specific product anyway so you are still left with an estimate. What I did with your samples was to use the new unused values of the new oil as the baseline and subtracted them from the readings of the used oil. I did not adjust any of the new oil values."

 

[Gokhan]

VOA results with the oxidation reported (subtract it from itself as a baseline to result in zero as I explained above). The sulfation and nitration baseline values are recorded in the post above:

 

[Blue_Angel]

Originally Posted By: Blue_Angel
Originally Posted By: Blue_Angel
...what would happen to KV measurements if they were taken using increasing pressures to force the oil through the test orfice? Would we present "higher" shear conditions, the trend line of which may or may not point in the general direction of the HTHSV spec?


Anyone with any thoughts on this?


Originally Posted By: Shannow
Orifices aren't the best way of measuring viscosity, as there needs to be a shearing action (velocity gradient)...traditionally carried out via a capillary (small tube).

Problem is that the velocity profile of a tube is a bear to calculate from first principals (calculus - infinite flat plates were easier), and gives different shear rates across the tube.

But yes, in theory, if you were to take a big syringe and keep increasing the pressure, you would see an increasing pressure to get the fluid out (velocity/shear) faster, until a point is reached that the increase in pressure to get a further increase in velocity doesn't match (is lower) than what you were used to.

This point is where the fluid VIIs start to "straighten out" and don't increase the viscosity like they did...a straight weight (e.g. SAE30) wouldn't display this kick.


Shannow, your response is right in line with how this phenomena is explained on Page 4 of this Savant Labs paper, "The Expanding Dimensions of High Shear rate Viscometry":

http://www.savantlab.com/images/TBS_Paper_-_SAE_2008-01-1621_The_Expanding_Dimensions....pdf

From the paper:

"As shown in Figure 6, in capillary viscometry, at a given flow rate, shear rate is not constant but rather ranges from maximum value at the wall to zero at the peak of the presumed parabolic flow profile. Note that the flow profile of polymer-containing oils is not parabolic as a consequence of the effect of the varying shear rates across the tube on the polymer coil. This limits high shear rate studies of polymeric solutions in oil."

They were unable to accurately corelate high shear viscosity results from a high-pressure capillary viscometer with the results from the TBS viscometer, though as you said, the change to the 2nd Newtonian phase was taking place, just not consistently through the entire oil volume as it does between shear plates.

Somebody way back when had the same train of thought I did and was able to disprove the idea with theory backed up by experimentation. Cool.