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

[Blue_Angel]

This is a great thread guys, I hope it keeps going for a while!

Question regarding KV vs HTHS. At what point does oil flow go from KV scenario to HTHSV scenario?

Thoughts:

An oil galley in the block whose purpose is to transport oil from point A to point B will have a relatively low oil velocity and low overall oil shear. Properly sized, this type of flow environment would produce minimal restriction related oil pressure rise.

At the end of that galley is a restriction orfice who's purpose is to control oil flow by introducing a significant restriction and therefore cause a pressure increase. Inside that orfice, oil velocity increases dramatically as does shear.

KV is measured under the force of gravity only AFAIK, and would present an extremely low-shear environment. Every oil flow restriction in the engine has the operating oil pressure behind it forcing oil through at relatively high velocity.

Comments here suggest that engineered flow restrictions other than journal bearings correlate only to the KV oil specs. Is this really the case, or does the higher shear environment of an oil restriction present to the oil something IN-BETWEEN the KV and HTHSV test environments? i.e. 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?

I realize it would take higher than normal operating pressures to reach the shear rates seen in journal bearings, just wondering about the potential of a trend line that may point in that direction and how far along that line our engine's oil flow restrictions are actually operating.

 

[Gokhan]

Originally Posted By: Blue_Angel
Another nit-pick:
Originally Posted By: Gokhan
If the bearings are the main resistance to the oil flow, they will be the main contribution to the oil pressure.

If the main bearings are the main resistance to oil flow, they will NOT be the main contributor to oil pressure. The most free-flowing part of the oil flow path will have the largest effect on oil pressure.

This could be counterintuitive if you don't consider the right analogy.

An excellent analogy is the electric-circuit equivalent of the fluid circuit. Oil pump is the power supply; oil flow is the current, and pressure drop is the voltage drop. Sum of the pressure drops (voltage drops) around the oil-flow (current) circuit equal the pressure (voltage) generated by the power supply (oil pump). Largest pressure (voltage) drops occur at the largest resistances. Largest resistances in an oil-flow circuit are the thinnest and longest paths. If a pipe is thick, very little pressure drop is needed to move the oil through it, just like very little voltage drop is needed to push current through a thick conductor.

 

[Gokhan]

Originally Posted By: Shannow
Originally Posted By: Gokhan
My understanding of HTHSV150 has been that it applies more to high-load situations where the minimum oil-film thickness (MOFT) is very small and the temperature at the MOFT instantaneously reaches 150 C or so due to adiabatic heating from the instantaneously rising pressure. In other words, HTHSV150 is more of a measure of wear protection at extreme conditions than a measure of viscosity for more normal conditions.

Temperature rise in the oil film is due to the frictional work applied to the oil...adiabatic heating is only applicable to compressible fluids like gasses, not incompressible liquids.

HTHS is an attempt at viscosity measurement under high shear...it would be better carried out at the Walmart spec sheet I posted of 100C than 150C, I agree, but if the fluid is again in the second Newtonian range, HTHS is going to be a much better predictor of the high shear viscosity at 120C than any KV is likely to be.

You're certainly right that I didn't consider the incompressibility. Work done is force times displacement or pressure times volume change; so, no volume change results in no work done or no energy added to the fluid to raise its temperature through adiabatic heating.

CATERHAM was brave/reckless enough to run his tests at 6500 rpm. Who would run his engine at 6500 RPM? At that RPM, I can see that the bearing temperatures can reach near 150 C.

What do you think is the normal operating temperature of the bearings at normal loads and RPMs?

 

[Blue_Angel]

Originally Posted By: Gokhan
Originally Posted By: Blue_Angel
Another nit-pick:
Originally Posted By: Gokhan
If the bearings are the main resistance to the oil flow, they will be the main contribution to the oil pressure.

If the main bearings are the main resistance to oil flow, they will NOT be the main contributor to oil pressure. The most free-flowing part of the oil flow path will have the largest effect on oil pressure.

This could be counterintuitive if you don't consider the right analogy.

An excellent analogy is the electric-circuit equivalent of the fluid circuit. Oil pump is the power supply; oil flow is the current, and pressure drop is the voltage drop. Sum of the pressure drops (voltage drops) around the oil-flow (current) circuit equal the pressure (voltage) generated by the power supply (oil pump). Largest pressure (voltage) drops occur at the largest resistances. Largest resistances in an oil-flow circuit are the thinnest and longest paths. If a pipe is thick, very little pressure drop is needed to move the oil through it, just like very little voltage drop is needed to push current through a thick conductor.


Wire a 10 ohm resistor (low resistance) in parallel with a 100 ohm resistor (high resistance) and connect them to a power supply. The 10 ohm resistor will have 10 times as much current passing through it as the 100 ohm resistor will.

Your comment is true for a series circuit, but an engine's oil system is not a series circuit, it is a parallel circuit.

 

[Gokhan]

Originally Posted By: Blue_Angel
Originally Posted By: Gokhan
Originally Posted By: Blue_Angel
Another nit-pick:
Originally Posted By: Gokhan
If the bearings are the main resistance to the oil flow, they will be the main contribution to the oil pressure.

If the main bearings are the main resistance to oil flow, they will NOT be the main contributor to oil pressure. The most free-flowing part of the oil flow path will have the largest effect on oil pressure.

This could be counterintuitive if you don't consider the right analogy.

An excellent analogy is the electric-circuit equivalent of the fluid circuit. Oil pump is the power supply; oil flow is the current, and pressure drop is the voltage drop. Sum of the pressure drops (voltage drops) around the oil-flow (current) circuit equal the pressure (voltage) generated by the power supply (oil pump). Largest pressure (voltage) drops occur at the largest resistances. Largest resistances in an oil-flow circuit are the thinnest and longest paths. If a pipe is thick, very little pressure drop is needed to move the oil through it, just like very little voltage drop is needed to push current through a thick conductor.


Wire a 10 ohm resistor (low resistance) in parallel with a 100 ohm resistor (high resistance) and connect them to a power supply. The 10 ohm resistor will have 10 times as much current passing through it as the 100 ohm resistor will.

Your comment is true for a series circuit, but an engine's oil system is not a series circuit, it is a parallel circuit.

I'm glad that you understand electric circuits, especially the series and parallel connections, which is needed to understand the oil flow.

While you're right that there are parallel elements (such as valve train in parallel to the bearings), I think main flow happens through the bearing circuit (lowest resistance), which is the main factor in determining the oil pressure for that reason. When I said that the bearings had large resistance before, I meant with respect to the oil passages, not with respect to the valvetrain lubrication system.

So, CATERHAM is probably right that bearings are where the oil pressure is mostly determined.

You can see this paper for some info but there is not much detail.

 

[Shannow]

Originally Posted By: Gokhan
What do you think is the normal operating temperature of the bearings at normal loads and RPMs?


I've stated in the past (and been pooh-poohed as not "feeling right") that it's 10-40C above bulk oil temperatures.

When doing bearing calculations from scratch, you assume a rise of 15-20C (if that is typical), do an iteration of the power consumption, and revise the temperature estimate.

Bear in mind that if the bulk oil is (say) 80, and the bearing proper is 100, the oil exit temperature is 120.

Good article from Ricardo
http://www.ricardo.com/Documents/Downloads/pdf/ringpak_comparison_of_predicted.pdf

Some information fro a car mag.

http://www.chevyhiperformance.com/tech/engines_drivetrain/shortblock/4380_bearing_clearance_info/

Interesting point (that I'll keep making) is that as manufacturers go to thinner oils, they are widening bearings, and reducing clearances...which increases the frictional losses, while stiffening the bearing.

 

[JerryBob]

Uhm - so, is this a good oil or not? I run it in my Tacoma, but have yet to do a UOA on it. I have 2 UOA's on Mobil AFE 0w20 and they came back very sweet.

I bought a case of TGMO online at midatlantictoyotaparts.com at a pretty good price.

 

[buster]

It's good, but nothing to get too excited about. Mobil 1 is going to offer better high temperature protection and oxidation resistance due to the better base oils used.

Mobil 1 EP 0w20 has been tested by XOM out to 20k miles.

If squeezing another fraction of a percent out of your mpg is what you want, go with the TGMO.

 

[Gokhan]

Originally Posted By: JerryBob
Uhm - so, is this a good oil or not? I run it in my Tacoma, but have yet to do a UOA on it. I have 2 UOA's on Mobil AFE 0w20 and they came back very sweet.

I bought a case of TGMO online at midatlantictoyotaparts.com at a pretty good price.

Looking forward to your UOA comparison with M1 AFE 0W-20 SN!

Price at about $6 per quart is not bad!

 

[JerryBob]

Originally Posted By: Gokhan
Originally Posted By: JerryBob
Uhm - so, is this a good oil or not? I run it in my Tacoma, but have yet to do a UOA on it. I have 2 UOA's on Mobil AFE 0w20 and they came back very sweet.

I bought a case of TGMO online at midatlantictoyotaparts.com at a pretty good price.

Looking forward to your UOA comparison with M1 AFE 0W-20 SN!

Price at about $6 per quart is not bad!



Definitely will do a UOA with TGMO. I would be surprised if there was much of a difference.

I would not run TGMO if I wasn't able to find it economically. That website is geographically pretty close, so shipping is cheap and fast.

 

[Gokhan]

Originally Posted By: JerryBob
Originally Posted By: Gokhan
Originally Posted By: JerryBob
Uhm - so, is this a good oil or not? I run it in my Tacoma, but have yet to do a UOA on it. I have 2 UOA's on Mobil AFE 0w20 and they came back very sweet.

I bought a case of TGMO online at midatlantictoyotaparts.com at a pretty good price.

Looking forward to your UOA comparison with M1 AFE 0W-20 SN!

Price at about $6 per quart is not bad!

Definitely will do a UOA with TGMO. I would be surprised if there was much of a difference.

I would not run TGMO if I wasn't able to find it economically. That website is geographically pretty close, so shipping is cheap and fast.

Good find indeed! Actually they even ship very cheap all the way to California.

Fortunately I can get it even cheaper from the local dealers here. There is Carson Toyota about 25-mile away from whom I can order online and pick up will-call and another dealer only 1-mile away from whom I can have a price match by showing the online price of the other dealer.

 

[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?

 

[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.

Bearings operate in a regime typically above this high shear rate (regardless of temperature), so the "high shear" viscosity is more representative than the straight KV values (they work in oil galleries etc., as per Gokhan's previous posts), so the High Shear 120 (or whatever the mean temperature is) is more appropriate than the KV120.

If we had a High Shear VI, all would be sweet...but we don't (some here believe that they can translate the KV VI across to the HTHS range and come up with a high shear viscosity at any temperature, but as the VIIs are in temporary shear, I disagree with that assertion)...so we are stuck with HTHS at 150C and a million per seconds as the only nearly appropriate parameter to work with.

Fun read (not quite off topic)

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

 

[Garak]

Originally Posted By: Shannow
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.

Oh, be a sport. At least show us an integral for flux or something similarly fun.

And Gokhan, when I get some free time after I deal the year ends of my businesses, I'm going to be calling you out on the carpet over the function you posted a page or two back. Was that function derived by graphical analysis? I'd like to see the derivation of that.

 

[Gokhan]

Originally Posted By: Garak
And Gokhan, when I get some free time after I deal the year ends of my businesses, I'm going to be calling you out on the carpet over the function you posted a page or two back. Was that function derived by graphical analysis? I'd like to see the derivation of that.

You mean the exponential function for viscosity? It's a simple two-point fit. You have two equations -- a*exp(-b*T) calculated for KVT1 and KVT2 -- and two unknowns -- a and b of the exponential function -- and you can determine these two unknowns from the two equations. You can verify that it works by calculating KV40 and KV100 by plugging in a, b, and T.

Derivation is fairly simple. You just take the ln of both sides of the equation -- ln[a*exp(-b*T)] = ln(KVT) and then it becomes a simple linear equation -- ln(a) - b*T = ln(KVT). That gives you ln(a) = ln(KVT) + b*T. You then take the exp and get a = KVT*exp(b*T). To get b, you divide the equation calculated at T1 by the one calculated at T2 and then take ln of both sides. So, ln[KVT1/KVT2] = ln[exp(-b*T1)/exp(-b*T2)], resulting in ln(KVT1) - ln(KVT2) = -b*T1 + b*T2, resulting in ln(KVT1) - ln(KVT2) = b*(T2-T1), resulting in b = [ln(KVT1)-ln(KVT2)]/(T2-T1).

 

[Gokhan]

Originally Posted By: Gokhan
You just take the ln of both sides of the equation -- ln[a*exp(-b*T)] = ln(KVT) and then it becomes a simple linear equation -- ln(a) - b*T = ln(KVT). That gives you ln(a) = ln(KVT) + b*T. You then take the exp and get a = KVT*exp(b*T).

Actually, to get a, you simply divide by the exp. When I was typing on the fly, I made it more complicated than it is.

 

[Garak]

When I get some time in a while (after the year end of my businesses), I'm going to see if I can simplify that function a bit. Aesthetically, that could give a mathematician a stroke.

 

[fpracha]

Originally Posted By: Gokhan
If the bearings are the main resistance to the oil flow, they will be the main contribution to the oil pressure. (This is clearly not the case in old engines where bearings aren't pressurized.) You're right that high-shear viscosity is probably more appropriate for the bearings because of the temporary shear of VII molecules. There are other contributions (paths) to oil flow as well and oil pressure will not entirely be determined by the bearings.

Then how come the TGMO 0w-20 is giving classically superb results in your old toyota engine (1985 Corolla LE), in fact better than the 30 and 40 multigrade "more strongly additized" previously used engine oils in your very own long experience ?

Originally Posted By: Gokhan
For this reason, a temperature-dependent viscosity is more appropriate in my opinion to judge oil pressure. To me, it looks like TGMO has less oil pressure simply because it's much thinner at 80 - 85 C due to its ultra-high VI than other oils. You can use the spreadsheet I provided above to calculate the viscosity as an exponential function of temperature.

My understanding of HTHSV150 has been that it applies more to high-load situations where the minimum oil-film thickness (MOFT) is very small and the temperature at the MOFT instantaneously reaches 150 C or so due to adiabatic heating from the instantaneously rising pressure. In other words, HTHSV150 is more of a measure of wear protection at extreme conditions than a measure of viscosity for more normal conditions.


Does this really imply that for engines where 5W-30 oils are specified:
...We can use high VI 0w-30 grade oils and by extrapolation logic above a high VI 0w-20 engine oil is more than adequate for all such engines (since the HTHSV150 of "high VI 0w-30 grade oils" is in excess of required in modern engines ; while HTHSV150 of "high VI 0w-20 grade oils" is sufficiently positioned at the 2.6cSt minimum value) ???

 

[Blue_Angel]

Just a thought/question regarding the real world (ie high shear) VI of an oil. IF (and a big if) journal bearings represent the main contribution to the operating oil pressure of an engine, could we not plot oil pressure vs temperature for different oils in the same engine and get a sort of HTHS plot?

For example, plotting for two different oils (example Mobil 1 5w-30 and TGMO 0w-20), one having a much higher VI than the other, would we not be able to use a trend line from gathered data to see at which temperature those two oils would have effectively the same viscosity? It would require strict engine RPM control (like a vehicle on stands in gear with the cruise control set), and for the vehicle to have both oil temperature and pressure gauges.

We would be able to plot the ACTUAL viscosity change with temperature in high shear conditions.

 

[Gokhan]

I have e-mailed the question by CATERHAM and others to WearCheck USA and got an answer.

Question: There has been some controversy on the viscosity index of TGMO 0W-20 SN virgin oil among the oil folks on the Internet (Bob is the Oil Guy forum in particular). Could the KV40, KV100, and VI numbers on the virgin oil be retested or do you have absolute confidence in these numbers?

Answer: I read the Bobs the Oil Guy forum, though I’m not crazy about the forums. We do redundant testing on all new oils, so I am very confident in the results.

So, it looks like TGMO 0W-20 SN is the viscosity-index champion with its VI = 236, easily beating Eneos Sustina 0W-20 SN.