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#4808624 - 07/08/18 07:53 PM Flash point, base oil quality, performance
d00df00d Offline


Registered: 10/20/05
Posts: 11271
Loc: PA
I always thought there was generally a strong correlation between an engine oil's flash point and the quality of its base stocks, such that an oil with a higher flash point could generally (though not always) be expected to be more resilient at high temps: less shear, fewer deposits, etc. I fully expected there to be exceptions, but I thought that was more-or-less the general trend.

Now I feel like I might have been wrong about that. On the one hand, Castrol Edge Supercar HP -- their Indy Car oil -- has a flash point of 220 C; Mobil 1 FS 0W-40 is at 226 C; and most (all?) of the Pennzoil Ultra line is below 230 C, with some oils only just above 200 C. On the other hand, the dino 5W-20 I'm running now has a flash point of 230 C, and Idemitsu makes an $8/qt 10W-30 with a flash point of 260 C.

Is there no correlation between flash point and base oil quality? Can anything about an engine oil's performance be reasonably inferred from its flash point? If so, what?
_________________________
2011 Mazda RX-8 R3
Mobil Super 5w-20

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#4808679 - 07/08/18 09:15 PM Re: Flash point, base oil quality, performance [Re: d00df00d]
Tom NJ Offline


Registered: 07/27/06
Posts: 2124
Loc: Virginia
The problem with flash point is the test reproducibility by ASTM D 92 is +- 9C (+- 16F). To this test reproducibility you need to add batch-to-batch variability, which can give quite a range to the formulation. In addition, the figure published by the manufacturer for the formulation may be the average of their batch data, or the highest, or even the lowest.

In my day I ran thousands of flash points, and monitored lab data on thousands more so I could report an accurate average on our ester data sheets. I knew exactly what the flash point should be for a given pure ester, yet the flash points listed on competitor data sheets for the same ester were all over the place.

If you had a true flash point on the motor oil base oils, I would expect some correlation to base oil quality within a given chemistry, but when you start blending base oil chemistry and adding additives, all bets are off - too many variables. For example, a 4 cSt Group I stock has a flash point of around 400F while a 4 cSt PAO is about 425F, a diester about 440F, and a POE 480F. These differences make it difficult to compare unknown blends.

Noack volatility on the finished motor oil is probably a better measure of base oil quality since it isolates volatility from flammability, but even here there are many variables. For all the above reasons I pretty much ignore flash points.


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#4808699 - 07/08/18 09:39 PM Re: Flash point, base oil quality, performance [Re: d00df00d]
CT8 Offline


Registered: 10/09/14
Posts: 11224
Loc: Idaho
Thanks TOM
_________________________
"Don't let your preconceived notions get in the way of facts."
Geoff Metcalf

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#4808760 - 07/09/18 01:25 AM Re: Flash point, base oil quality, performance [Re: d00df00d]
OilUzer Offline


Registered: 07/31/17
Posts: 169
Loc: WA
How did Noack came up with 250C?
Or who came up with 250C?I

Do we want the Noack test temperature (250C = 482F) be above most (all?) oil flash points to be an effective test or does it matter at all?

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#4808814 - 07/09/18 06:12 AM Re: Flash point, base oil quality, performance [Re: Tom NJ]
d00df00d Offline


Registered: 10/20/05
Posts: 11271
Loc: PA
Originally Posted By: Tom NJ
The problem with flash point is the test reproducibility by ASTM D 92 is +- 9C (+- 16F). To this test reproducibility you need to add batch-to-batch variability, which can give quite a range to the formulation. In addition, the figure published by the manufacturer for the formulation may be the average of their batch data, or the highest, or even the lowest.

In my day I ran thousands of flash points, and monitored lab data on thousands more so I could report an accurate average on our ester data sheets. I knew exactly what the flash point should be for a given pure ester, yet the flash points listed on competitor data sheets for the same ester were all over the place.

If you had a true flash point on the motor oil base oils, I would expect some correlation to base oil quality within a given chemistry, but when you start blending base oil chemistry and adding additives, all bets are off - too many variables. For example, a 4 cSt Group I stock has a flash point of around 400F while a 4 cSt PAO is about 425F, a diester about 440F, and a POE 480F. These differences make it difficult to compare unknown blends.

Noack volatility on the finished motor oil is probably a better measure of base oil quality since it isolates volatility from flammability, but even here there are many variables. For all the above reasons I pretty much ignore flash points.


Thanks, Tom!

As a largely-academic aside: is there ever a case where a tougher base oil is less volatile but not less flammable?
_________________________
2011 Mazda RX-8 R3
Mobil Super 5w-20

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#4808851 - 07/09/18 07:35 AM Re: Flash point, base oil quality, performance [Re: d00df00d]
Tom NJ Offline


Registered: 07/27/06
Posts: 2124
Loc: Virginia
Originally Posted By: d00df00d

Thanks, Tom!

As a largely-academic aside: is there ever a case where a tougher base oil is less volatile but not less flammable?


Yes, different chemistries may have different flammabilities. For example phosphates would be less flammable at a given viscosity that say a hydrocarbon. There may also be flammability differences between linear hydrocarbons and aromatic hydrocarbons or esters or metal containing additives, but I do not have data on this. Molecular weight distribution is also a factor. The flash point test gathers oil vapors in the space above the oil surface, mixes the vapors with air and attempts to ignite the vapor/air mixture with a flame. The Noack test sweeps the vapors away making it a more pure volatility test. Since both tests are substantially affected by volatility there is a correlation but I wouldn't expect it to be perfect since there is no flame involved in the Noack (not to mention different temperature profiles).

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#4808864 - 07/09/18 07:58 AM Re: Flash point, base oil quality, performance [Re: OilUzer]
Tom NJ Offline


Registered: 07/27/06
Posts: 2124
Loc: Virginia
Originally Posted By: OilUzer
How did Noack came up with 250C?
Or who came up with 250C?I

Do we want the Noack test temperature (250C = 482F) be above most (all?) oil flash points to be an effective test or does it matter at all?


I don't know who decided on 250C - hopefully it was correlated to some real world performance parameter as all tests should be, but I have also seen what I call "management by round numbers".

Noack and flash point are quite different. Noack evaporates the light ends of an oil by blowing air across the surface at a constant 250C and measures the weight loss of the sample. Flash point slowly heats the oil from ambient to the point at which the vapors give a flash when a flame is passed over. The flame is not applied until the oil is within 27C of the expected flash point, so much of the light ends are already evaporated off. If you added say 5% of a solvent to an oil, the Noack loss would go up by 5% since all of the solvent would be evaporated off under the conditions of the test. The flash point, however, would not be affected since the solvent would be evaporated off before the flame is passed over the oil surface.

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#4808866 - 07/09/18 08:00 AM Re: Flash point, base oil quality, performance [Re: d00df00d]
Virtus_Probi Offline


Registered: 06/25/15
Posts: 4054
Loc: New England
Just wanted to mention that I find Tom NJ's contributions here to be very valuable and I always keep an eye out for his posts.
Thanks so much for sharing from your wealth of oil industry knowledge, Tom NJ!
_________________________
2014 Forester XT, 86000 miles
Last Change;
M1 5W30 d1G2
Tokyo Roki 15208AA170 filter

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#4808898 - 07/09/18 08:40 AM Re: Flash point, base oil quality, performance [Re: Virtus_Probi]
carviewsonic Offline


Registered: 08/17/16
Posts: 226
Loc: Alberta
"Just wanted to mention that I find Tom NJ's contributions here to be very valuable and I always keep an eye out for his posts.
Thanks so much for sharing from your wealth of oil industry knowledge, Tom NJ!"

+1
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'18 Impala new
'03 Park Avenue 300k kms
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#4808907 - 07/09/18 08:51 AM Re: Flash point, base oil quality, performance [Re: d00df00d]
Tom NJ Offline


Registered: 07/27/06
Posts: 2124
Loc: Virginia
Thanks! Since I am retired for 11 years now I have to do something with all this useless knowledge floating around in my head before it all fades away! grin2

Now out to the garden to harvest some garlic, onions, peppers and beans.

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#4808909 - 07/09/18 08:51 AM Re: Flash point, base oil quality, performance [Re: Virtus_Probi]
d00df00d Offline


Registered: 10/20/05
Posts: 11271
Loc: PA
Originally Posted By: Virtus_Probi
Just wanted to mention that I find Tom NJ's contributions here to be very valuable and I always keep an eye out for his posts.
Thanks so much for sharing from your wealth of oil industry knowledge, Tom NJ!

Seconded! cheers
_________________________
2011 Mazda RX-8 R3
Mobil Super 5w-20

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#4809006 - 07/09/18 10:23 AM Re: Flash point, base oil quality, performance [Re: d00df00d]
bluesubie Offline


Registered: 08/04/03
Posts: 2288
Loc: NJ
I wish there was an applause emoticon but Tom will have to settle for thumbsup .

cheers
_________________________
'04 Subaru Forester 2.5XT
Castrol Edge 0W-40

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#4809027 - 07/09/18 10:41 AM Re: Flash point, base oil quality, performance [Re: Tom NJ]
Virtus_Probi Offline


Registered: 06/25/15
Posts: 4054
Loc: New England
Originally Posted By: Tom NJ
Thanks! Since I am retired for 11 years now I have to do something with all this useless knowledge floating around in my head before it all fades away! grin2
Now out to the garden to harvest some garlic, onions, peppers and beans.

What time is lunch? I'm all for some fresh produce...
;^)
Sounds like you have found new ways to be productive in your retirement!
_________________________
2014 Forester XT, 86000 miles
Last Change;
M1 5W30 d1G2
Tokyo Roki 15208AA170 filter

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#4809089 - 07/09/18 11:36 AM Re: Flash point, base oil quality, performance [Re: bluesubie]
4WD Offline


Registered: 09/21/10
Posts: 6532
Loc: Texas
Originally Posted By: bluesubie
I wish there was an applause emoticon but Tom will have to settle for thumbsup .

cheers
Cheers2

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#4809102 - 07/09/18 11:41 AM Re: Flash point, base oil quality, performance [Re: Virtus_Probi]
Tom NJ Offline


Registered: 07/27/06
Posts: 2124
Loc: Virginia
Originally Posted By: Virtus_Probi

What time is lunch? I'm all for some fresh produce...
;^)
Sounds like you have found new ways to be productive in your retirement!


Retirement is so busy that I don't know where I ever fund the time to work! Been growing vegetables for over 40 years, just on a larger scale now. Lunch is beet salad with onions, blue cheese, and walnuts. Better hurry over!

Oh, and I brew beer! cheers


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