Are thinner oils about fuel economy or tighter engines?

[RDY4WAR]

There's merit to higher viscosity, and thus higher aniline point, reducing solubility. It's just not the only parameter that affects solubility. Focusing on a single parameter can get you lost in a rabbit hole of misconceptions. I've been in that rabbit hole myself. You have to look at the oil as a whole.

Discussions on single parameters can be fun though. I'm curious of the affect VII has on the aniline point and solubility. Say you have a 0W-20 with blends of 2/4/6 cSt base oil and a bit of VII compared to a 10W-20 with straight 8 cSt base oil and no VII. At the same KV100 and same group base oil from the same source, would one have better solubility than the other? What about the carrier for the additive package? Most add packs are blended in a group I carrier though some are in group III. How do you factor that into the equation? Some additives like ZDDP are synthetic esters. How do they impact the solubility? What's the effect on specific gravity, volatility, aeration, and oxidation? Does solubility decrease as an oil becomes aerated or as it ages and oxidizes? There's a ton of factors to consider.

 

[MolaKule]

@ArthurArgentum "To clarify, I did not state that Hildebrand's theory directly incorporates viscosity."​

But this is what you have been esoterically arguing all along, see Post #103.

Einstein's result for the diffusion coefficient D of a spherical particle of radius a in a fluid of dynamic viscosity h at absolute temperature T is:

thus, the Einstein-Stokes equation describes diffusion of particles in a fluid at temperature T.

The modified Nernst-Brunner equation is:

dm/dt=DA(t)L(Cs−Cb)=kcA(t)(Cs−Cb),

where m is the total dissolved mass, A is the total exposed surface area of the dissolving particle at time t, D is the diffusion coefficient of the solute in the solvent, L is the thickness of the boundary layer of unstirred solvent surrounding the particle, Cs is the solubility of the solvent in the solute (the highest possible solute concentration in the solvent at present conditions), and Cb is the mass concentration of the dissolved species in the entire solvent volume under consideration. In the alternate construction of the Nernst-Brunner equation also shown, the diffusion coefficient D and boundary layer thickness L are replaced by mass transfer coefficient kc = D/L. Thus, the rate of mass removal by diffusion from a dissolving object is proportional to the exposed surface area, so solute physical structures with more surface area, such as powders, will dissolve faster than those with less surface area, such as single objects, if all other factors such as solvent volume and environmental conditions are the same. However, material properties and environmental factors play an important role; a higher diffusion coefficient for the solute in the solvent increases the rate of mass removal, and as the bulk concentration of solute in the entire solution approaches the solubility limit, the rate of approaches zero.

Now please show how you are combining the Hildebrands, Hansen, Stokes - Einstein, and Nernst - Brunner equations to support your hypothesis.

 

[ArthurArgentum]

Discussions on single parameters can be fun though. I'm curious of the affect VII has on the aniline point and solubility. Say you have a 0W-20 with blends of 2/4/6 cSt base oil and a bit of VII compared to a 10W-20 with straight 8 cSt base oil and no VII. At the same KV100 and same group base oil from the same source, would one have better solubility than the other? What about the carrier for the additive package? Most add packs are blended in a group I carrier though some are in group III. How do you factor that into the equation? Some additives like ZDDP are synthetic esters. How do they impact the solubility? What's the effect on specific gravity, volatility, aeration, and oxidation? Does solubility decrease as an oil becomes aerated or as it ages and oxidizes? There's a ton of factors to consider.

I agree with you, there is still much to discuss. I was simply seeking valuable insights (one major and one minor option) for reducing viscosity, and I am pleased to have shared my findings

 

[Astro14]

It appears that there has been a misinterpretation, as you have not carefully read and understood my previous statements. Allow me to reiterate and clarify. I am specifically referring to the average market segment, where oils with viscosities such as 5W-40 or 0W-40 are commonly found for thick PCMO. These oils are typically composed of hydrocarbon oils based on highly refined and saturated base oils, and occasionally PAOs, with a limited (very limited in average) amount of esters (often they don't contain at all). This is the reality within this market segment.
In this context, such oils formulated with a base with KV100 viscosity of 6 cSt (4+6, rare - 8) are often augmented with a significant proportion of thickener, which can be a mechanically resistant polymer. The topic of shear stable polymers and their thickening abilities is indeed a separate and extensive discussion. It is worth noting that the thickening ability of low-SSI polymers is generally lower, necessitating a higher dosage for effective thickening.
These are the oils that are commonly available and presented in the average market. It is essential to understand that my previous statements were made in the context of a comparative formulations reflecting the average formulation practices within the industry. Therefore, I kindly urge you to read my statements attentively before engaging in further discussion or argumentation.

I have read your statements. Completely. I do not misinterpret. I disagree.

Do not ascribe my disagreement to lack of understanding, comprehension, or care on my part.

That's the ad hominem argument - the last refuge of a weak position.

 

[RDY4WAR]

I want to note that I base my position on data showing higher aniline points with higher base oil viscosity (as has been posted in this thread) and articles stating how solubility changes with the aniline point.

"Aniline point is generally considered as a measure of oil solubility: the lower the aniline point of an oil, the higher its solubility. From a theoretical viewpoint, aniline point can be defined as the temperature, at which the solubility of aniline in oil (or oil in aniline) reaches 50 vol.%"

https://www.sciencedirect.com/science/article/abs/pii/S0016236107000981#:~:text=Aniline%20point%20is%20generally%20considered,in%20aniline)%20reaches%2050%20vol.

I'm also curious as to how solubility of different base oils is affected by blending. Say you make a blend that's 10% adipate ester, let's say it's Esterex A51 with an aniline point of ~20°C, and blend it with the remaining 90% as a 6 cSt PAO, let's say it's SpectraSyn 6 with an aniline point of 126°C. Is it a simple math problem of (126°C x 9 + 20°C) / 10 = aniline point of blend? (115°C) Is it much more complicated than that? (I'm guessing so)

 

[ArthurArgentum]

Stokes - Einstein, and Nernst - Brunner equations to support your hypothesis.

By combining these two formulas, it becomes evident that the dissolution rate (dm / dt, "speed") is influenced by D, which diminishes as viscosity η increases. Additionally, h represents the thickness of the stagnant solvent layer, which amplifies with higher viscosity.

the Hildebrands

I previously highlighted Hilderbrand's point in relation to aniline points, which serve as one of the five key indicators of solvent capacity. I substantiated my argument with illustrative examples and emphasized the following aspect:

 

[SaberOne]

I started out running Mobil 1™ 5W30 when new, and then I switched to Redline 5W20 for nearly 40k. At around 60k I switched to Maxima RS530 and have been there to present day. My OCI average has been 4k with an average ambient of 95 degrees. Summer temps average ~110+. During all this time, I’ve never seen any drop in oil level on the stick, and I was about ready to switch to RS1030, since my miles are stacking up, and we’re getting ready for another desert summer. Then I ran across this and contrasted that to what I read here on the forum.

 

[trgfunds]

For typical use I'm pretty sure that nobody is opposed to better fuel economy.

Hasn't it has been shown that these thinner oils do not actually improve fuel economy? Some are reporting *increases* in fuel economy going to a *higher/thicker* oil. Lots of chatter about this especially on the 0W16 Toyota front. Can anyone confirm?

 

[kschachn]

Hasn't it has been shown that these thinner oils do not actually improve fuel economy? Some are reporting *increases* in fuel economy going to a *higher/thicker* oil. Lots of chatter about this especially on the 0W16 Toyota front. Can anyone confirm?

No the physics are inescapable. A lower viscosity oil will lower fuel consumption.

Those chattering about it are also incapable of making proper measurements to make their conclusions. Such a measurement is utterly impossible in the real world.

 

[MolaKule]

@ArthurArgentum

"Solvency is impacted by several, somewhat-related, factors and can be assessed in terms of aniline point, viscosity index (VI), and viscosity-gravity constant(VGC). Aniline point, ASTM D611 [3], characterizes solvency via a compatibility test between the oil and aniline which is an aromatic amine. The lower the aniline point, the higher the solvency of the base oil. The VI, ASTM D2270 [4], which is a dimensionless number, is used to characterize the variation of the kinematic viscosity of a petroleum product with temperature. The VI correlates with chemical structure, with aromatics having the lowest VI, then naphthenics, and paraffins having the highest VI; therefore, a higher VI indicates a lower solvency. VGC, ASTM D2501 [5], describes the general relation between specific gravity and Saybolt viscosity. As the VGC increase, the solvency increases. VGC is often used in conjunction with aniline point since VGC is independent of molecular weight...."

From The Effect of Base Oils on Thickening and Physical Properties of Lubricating Greases from the STLE, Online as a PDF.

While this article is focused on greases and using naphthenics to increase solvency in greases, there are many other factors involved in solvency as the paper describes.

While the diffusion equation(s) above shows diffusion is directly related to Temperature and inversely proportional to viscosity, the Einstein–Smoluchowski equation, for diffusion of charged particles cannot be ignored:

Electrical Mobility equation.​

For a particle with electrical charge q, its electrical mobility μq is related to its generalized mobility μ by the equation μ = μq/q. The parameter μq is the ratio of the particle's terminal drift velocity to an applied electric field. Hence, the equation in the case of a charged particle is given as

where

is the diffusion coefficient (m2s−1

),

is the electrical mobility (m2V−1s−1

).

is the electric charge of particle (C, coulombs),

is the electron temperature or ion temperature in Kelvins.

cannot be ignored which is why, I think, my question in Post #92 went answered:

"So you're telling me that my 3.4 cSt Chevron PAO's have more solvency than my 8 cSt Hatcol PO esters? "

Focusing on one aspect of the physics of lubricating oils is analogous to saying, "Which lubricant has the greatest VI, or which lubricant has the least volitivity, or which oil has the most PAO, or..."

Focusing on one aspect ignores the totality of the formulation without realizing that maybe 100 factors have to be considered when formulating.

 

[OVERKILL]

I want to note that I base my position on data showing higher aniline points with higher base oil viscosity (as has been posted in this thread) and articles stating how solubility changes with the aniline point.

"Aniline point is generally considered as a measure of oil solubility: the lower the aniline point of an oil, the higher its solubility. From a theoretical viewpoint, aniline point can be defined as the temperature, at which the solubility of aniline in oil (or oil in aniline) reaches 50 vol.%"

https://www.sciencedirect.com/science/article/abs/pii/S0016236107000981#:~:text=Aniline%20point%20is%20generally%20considered,in%20aniline)%20reaches%2050%20vol.

I'm also curious as to how solubility of different base oils is affected by blending. Say you make a blend that's 10% adipate ester, let's say it's Esterex A51 with an aniline point of ~20°C, and blend it with the remaining 90% as a 6 cSt PAO, let's say it's SpectraSyn 6 with an aniline point of 126°C. Is it a simple math problem of (126°C x 9 + 20°C) / 10 = aniline point of blend? (115°C) Is it much more complicated than that? (I'm guessing so)

As I noted in the previous tangent on this subject, a 4cSt Group III having a lower aniline point than a 6cSt Group III totally ignores the fact that the solubility of both of them is extremely poor in the first place. Minutely better than awful is still extremely bad. This is why other bases are used to improve solubility as there has been a necessary push to less volatile base oils like GTL and PAO as oil approvals have gotten more rigorous.

For some aniline point comparison figures here:
Shell GTL 4cSt Group III: 120C
XOM SpectraSyn 4cSt PAO: 119.2C
XOM SpectraSyn 6cSt PAO: 126.1C
Yubase YU-6 6cSt Group III: 126C

On the other end of the spectrum:
XOM EsterexA34 3.2cSt: -9.8C
XOM EsterexNP343 4.3cSt: XOM Synnestic5 4.7cSt: 32C


So, GTL and PAO have essentially identical aniline points and Yubase Group III is right there too. They are all awful. Whether it's 6cSt or 4cSt, the difference is quite small and also explains why PCMO's in general don't do any cleaning beyond rinsing away sludge. Looking at the 2nd group, it's then obvious why esters and AN's are used to provide solvency and can actually clean-up deposits.

 

[ArthurArgentum]

"So you're telling me that my 3.4 cSt Chevron PAO's have more solvency than my 8 cSt Hatcol PO esters? "

Focusing on one aspect of the physics of lubricating oils is analogous to saying, "Which lubricant has the greatest VI, or which lubricant has the least volitivity, or which oil has the most PAO, or..."

Are thinner oils about fuel economy or tighter engines?

Always thought it was only about fuel economy but with better manufacturing techniques and wanting better performance squeezed out of engines could it involve tighter tolerances as well? Your thoughts? Well, thoughts of mine then :) When it comes to lubricants viscosity, there are several...

bobistheoilguy.com

and

Are thinner oils about fuel economy or tighter engines?

Show me some of those equations and corresponding test data showing what the temperature rise difference is with all factors held constant except for the oil viscosity. Your inquisitiveness about this minor advantage is noteworthy. However, it is crucial to acknowledge that this is a vast and...

bobistheoilguy.com

 

[ArthurArgentum]

Focusing on one aspect ignores the totality of the formulation without realizing that maybe 100 factors have to be considered when formulating.

Kindly, the essence of our discussion lies within a realm of intermediate considerations. To elucidate further, I invite you to revisit my initial statement where all the pertinent assumptions were provided. Thus, it is evident that our discourse remains grounded in a framework of average assumptions but in the middle was this -

Are thinner oils about fuel economy or tighter engines?

Show me some of those equations and corresponding test data showing what the temperature rise difference is with all factors held constant except for the oil viscosity. Your inquisitiveness about this minor advantage is noteworthy. However, it is crucial to acknowledge that this is a vast and...

bobistheoilguy.com

 

[ZeeOSix]

I appreciate your viewpoint, but I respectfully disagree with the notion that SAE16 and SAE40 oils behave identically at operating temperatures. Viscosity plays a vital role, as thinner oil tends to drain more rapidly, especially in confined spaces. While it is true that oil will eventually heat up and flow, we should also consider specialized cooling oils that require a low viscosity index to efficiently reduce viscosity, enabling swift movement.

To observe the real-time rate of inflow and runoff at -25°C, I recommend watching the following YouTube video.

That video showed that the 5W-30 they used pumped and flowed very well even at that low temperature of -25C (-13F). If it flowed that well at -25C, just think how well it flows by gravity at 100C (212F). I really don't see how you think there is any advantage of a thinner oil at 100C "flowing down by gravity" in any engine. Do you really think that a xW-20 at 100C somehow benefits the engine by "flowing down" a few milliseconds faster to the sump than a xW-50 at 100C? If so, why do you believe that?

The lowest pumpability limit for a 5W-xx is -35C per SAE J300, and obviously if they used a 0W-xx there might slight improvement, but I saw absolutely nothing in that cold start test with the 5W-30 that showed it was a problem. You do realize that if cold flow and lubrication was an issue in extremely cold weather there would be literally 1000s of destroyed engines every year, yet that does not happen if the proper "W" rating of oil is used. The SAE J300 came up with "W" ratings and CCS and MRV pumpability standards for a reason.

 

[ZeeOSix]

I started out running Mobil 1™ 5W30 when new, and then I switched to Redline 5W20 for nearly 40k. At around 60k I switched to Maxima RS530 and have been there to present day. My OCI average has been 4k with an average ambient of 95 degrees. Summer temps average ~110+. During all this time, I’ve never seen any drop in oil level on the stick, and I was about ready to switch to RS1030, since my miles are stacking up, and we’re getting ready for another desert summer. Then I ran across this and contrasted that to what I read here on the forum.

What was discussed in that video if pretty much what most say here on BITOG about viscosity. It'a a lot safer to go down in the W grade and up in the KV100 grade than it is to go up in the W grade (unless you verify the change in W rating is acceptable for your cold start-ups) and down in KV100 grade.

 

[ArthurArgentum]

Do you really think that a xW-20 at 100C somehow benifits the engine by "flowing down" a few miliseconds faster to the sump than a xW-50 at 100C? If so, why do you believe that?

Yes, I do. However, as previously stated, it is important to acknowledge that this advantage holds a relatively minor significance.

The lowest pumpability limit for a 5W-xx is -35C per SAE J300, and obviously if they used a 0W-xx there might slight improvment, but I saw absolutely nothing in that cold start test with the 5W-30 that showed it was a problem. You do realize that if cold flow and lubrication was an issue in extremely cold weather there would be literally 1000s of destroyed engines every year, yet that does not happen if the proper "W" rating of oil is used. The SAE J300 came up with "W" ratings and CCS and MRV pumpability standards for a reason.

The intent behind sharing the video was purely for amusement, as it provided an entertaining glimpse into real-life scenarios. No specific conclusions should be drawn from it, particularly since the your mention of a cold oil prompted its reference. No specific ideas or suggestions were put forth by me

 

[ZeeOSix]

Yes, I do. However, as previously stated, it is important to acknowledge that this advantage holds a relatively minor significance.

There is absolutely zero advantage of "gravity flow down" inside an engine when the oil is hot ... regardless of viscosity.

Exactly what is going to happen differently between a xW-16 and xW-50 at 100C in terms of lubrication to the engine due to the mere milliseconds of gravity flow down difference?

The intent behind sharing the video was purely for amusement, as it provided an entertaining glimpse into real-life scenarios. No specific conclusions should be drawn from it, particularly since the your mention of a cold oil prompted its reference. No specific ideas or suggestions were put forth by me

So a more enhanced Project Farm type of video? It did actually support my position ... there was absolutely nothing bad about how that oil flowed at the -25C (-13F) cold start-up, even though it was a 5W at that temperature. Now if they would have used a 20W-xx it would be a different outcome, but that would not be the proper "W" grade for a start-up at -25C.

 

[ArthurArgentum]

Exactly what is going to happen differently between a xW-20 and xW-50 at 100C in terms of lubrication to the engine due to the mere milliseconds of gravity flow down difference?

I've already discussed this; it relates to heat transfer and shows a slight improvement.

So a more enhanced Project Farm type of video? It did actually support my position ... there was absolulty nothing bad about how that oil flowed at the -25C (-13F) cold start-up.

I would like to reiterate my point once again. I shared the video in response to your mention of cold-oil-related aspects. My intention was simply to provide a visual representation of the actual scenario, purely for amusement purposes. I have no agenda to persuade or dissuade you on any matter. If you happen to have a different perspective and wish to engage in a discussion, please feel free to do so. However, I would like to clarify that my intent is to share my thoughts rather than engage in weird arguments

 

[RDY4WAR]

As I noted in the previous tangent on this subject, a 4cSt Group III having a lower aniline point than a 6cSt Group III totally ignores the fact that the solubility of both of them is extremely poor in the first place. Minutely better than awful is still extremely bad. This is why other bases are used to improve solubility as there has been a necessary push to less volatile base oils like GTL and PAO as oil approvals have gotten more rigorous.

For some aniline point comparison figures here:
Shell GTL 4cSt Group III: 120C
XOM SpectraSyn 4cSt PAO: 119.2C
XOM SpectraSyn 6cSt PAO: 126.1C
Yubase YU-6 6cSt Group III: 126C

On the other end of the spectrum:
XOM EsterexA34 3.2cSt: -9.8C
XOM EsterexNP343 4.3cSt: XOM Synnestic5 4.7cSt: 32C


So, GTL and PAO have essentially identical aniline points and Yubase Group III is right there too. They are all awful. Whether it's 6cSt or 4cSt, the difference is quite small and also explains why PCMO's in general don't do any cleaning beyond rinsing away sludge. Looking at the 2nd group, it's then obvious why esters and AN's are used to provide solvency and can actually clean-up deposits.

Absolutely. I didn't mean to hint at anything otherwise. However, this wouldn't be BITOG without a fair share of splitting hair.

 

[wwillson]

Kindly, the essence of our discussion lies within a realm of intermediate considerations.

Exactly what does that mean? The words are very pretty, but mean practically nothing. It seems to me that the essence of the discussion lies within the facts being discussed, not intermediate considerations.