Does oil NOACK volatility really matters that much?

jurko

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Since it is done under ASTM D5800 which says the oil is heated to 482°F for one hour with constant air flow over it and weight of oil is measured before and after. I've never seen my engine oil temp reach higher than 223°F even on hot 100°F day in summer. At this temperature the evaporation loss must be way lower? Why should I care about stated evaporation % loss of given oil when it is done at more than twice the max oil operating temperature I observed in my car or does it actually matter?
 

jurko

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Certain parts of the engine get very hot, say the underside of the piston for example, the ring land areas, and oil is exposed to these parts. So in theory, a less volatile oil will be less likely to burn off and leave deposits in these areas.
Thank you. That makes sense. So there's more to it than just observed oil temp.
 
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While that is true, I still wonder what is the highest temperature oil sees for any amount of time.
I doubt in a standard commuter vehicle driving at modest rpms that it approaches 450F.
The hottest area of a piston is ~500F.
So the oil cooling and lubricating the cylinder/piston walls is going to be a good bit cooler than that.
My guess is in most situations oil never sees greater than 400F.
 

jurko

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Would you be kind to explain what makes some oil blenders like Redline achieve such a low NOACK? For example 5W-30 has NOACK 5.3%.
 
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Oh, I see. So it's all about the quality of base oil. What about additive package? Does this also plays role in NOACK?
Expensive botique oils tend to use higher quality base oils that meet that are less volatile than mineral oil to start with and have a naturally high Viscosity index and don't need as much VII added, VIIs are usually the more volatile part of the oil.
 

OVERKILL

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Expensive botique oils tend to use higher quality base oils that meet that are less volatile than mineral oil to start with and have a naturally high Viscosity index and don't need as much VII added, VIIs are usually the more volatile part of the oil.

Actually, I believe VII's are low volatility, IIRC. It's the light bases used with the liberal dose of VII that burns off.

Looking at some light bases, Shell XHVI 4.0 is 15% Noack, and that's a "premium" Group III base.
 
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I read in a post here not long ago here that there is an inverse relationship with NOACK and engine cleanliness. Kind of knocked my socks off as it was counterintuitive but it was credible based on the poster. the jist was that lighter base oils are better at preventing deposits on lubricated areas than thicker oils. and I am a thicky
 
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Deposition throughout the engine in general doesn't occur like salt left in salines. One may try to pursue dryer intakes from the entry of PCV onwards (and lower consumption of course), but that's about it. More important areas and aspects of deposition may see opposing effects of lower volatility as well as of otherwise "higher quality" of base oils. Both not really new. Chasing Noack figure records is popular but more often than not it's primarily ignorant of most engine cleanliness aspects.
 

OVERKILL

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I read in a post here not long ago here that there is an inverse relationship with NOACK and engine cleanliness. Kind of knocked my socks off as it was counterintuitive but it was credible based on the poster. the jist was that lighter base oils are better at preventing deposits on lubricated areas than thicker oils. and I am a thicky

The Euro lubes, which have the strictest Noack limits, also have extremely tight regulation on deposit formation. And of course even the API caps Noack at 15%. When Shell first brought about their PurePlus based oils, which all had ridiculously low Noack volatility one of the claims the made was superior deposit prevention, as I'm sure you recall.

Noack is of course just one parameter; one test. But it's one that's common across both API and ACEA so obviously there's some importance to it, and keeping it relatively low.

I don't think it's coincidence that the oils that are most expensive to blend; use the most expensive base oils and are generally seen as "premium" also happen to have some of the lowest Noack volatility while the ones that are clearly bargain basement kiss the limits.

Should be obsess over Noack? No. As long as it's within the range specified for our application it is fine. Like pour point, it's just a little bit of an insight into how the oil is formulated and that makes it interesting :)
 
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On a side note, when I had asked Pennzoil for the Noack of their oils, I had two guys at two different times tell me they can't disclose that due to their additive supplier agreement.

A few things have happened in the last few months I've noticed - Mobil no longer reports HT/HS, Vavoline just gives a "<15%" Noack figure now and Pennzoil over time removed Noack completely.
 
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These tight regulations on deposit formation don't force into expensive base oils or such of low Noack volatility (they're reglementation of finished product performance to begin with ;-).

Noack values present a weight loss that was not even meant to represent volatile losses from thin films where some of the more important deposition takes place (more of a focus on constant oil levels, staying in grade and whatnot). Conradson carbon residues tend to rise with viscosity, thin film coker testing etc. shows it (viscosity is tightly connected with volatility, see Fig.4 https://www.bobistheoilguy.com/forums/threads/noack-vs-teost.330986/post-5506161 ),
" More volatile base stocks yield comparatively less deposits than heavier base stocks " e.g. they said in https://pdfslide.net/documents/depo...-surfaces-in-medium-prime-movers2003-cyl.html

Feel free to establish new rules of thumb but please try to ground them in a bit more than some Euro-Voodoo.
 
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OVERKILL

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These tight regulations on deposit formation don't force into expensive base oils or such of low Noack volatility (they're reglementation of finished product performance to begin with ;-).

I'm not sure what you are trying to say here 🤷‍♂️ The limit on Noack for the final product is what drives the use of higher quality, lower volatility base oils in order to stay within those limits, it isn't complicated. This is separate from the regulation and limits on deposit prevention and control, there are individual sequences for each. Many of the OEM sequences are even tighter on both deposit formation and Noack volatility so ultimately you end up with both as part of a finished product like M1 0w-40 for example.

Noack values present a weight loss that was not even meant to represent volatily losses from thin films where some of the more important deposition takes place. Conradson carbon residues tend to rise with viscosity, thin film coker testing etc. shows it (viscosity is tightly connected with volatility, see Fig.4 https://www.bobistheoilguy.com/forums/threads/noack-vs-teost.330986/post-5506161 ),
" More volatile base stocks yield comparatively less deposits than heavier base stocks " e.g. they said in https://pdfslide.net/documents/depo...-surfaces-in-medium-prime-movers2003-cyl.html

Feel free to establish new rules of thumb but please try to ground them in a bit more than some Euro-Voodoo.

It's not Euro voodoo, I'm not sure if we are having a communication breakdown, but it's clearly part of both the ACEA and API frameworks, with the ACEA limits (Euro) being more strict.

Regarding your links:

The lead-in on that 2nd link:
Screen Shot 2020-10-01 at 9.46.30 AM.png


We aren't talking about marine diesel engine liner deposits here, so I'm not sure what the claimed correlation is between that, and the use of higher quality, and thus lower volatility base oils in order to meet the ACEA limit of 13% or some of the OEM ones at <10% like Mercedes, which primarily applies to oils used in high speed gasoline-fuelled vehicles is 🤷‍♂️

Here's Lubrizol's breakdown of the ACEA protocols:

C4 has a limit of 11%.

Here's a brief overview of the use of Noack and the impact it has on the selection of base oils and why the more strict Noack limits have been imposed, which primarily relate to longer drain intervals:
 
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