Why the TEOST test is flawed....

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Back in 2006?, Honda came out with the HTO-06 (Hot Tube Test) which tested oils for turbo charger performance for deposit prevention. At the time few oils could meet it. You often see ASTM D6335, also known as the TEOST 33C test, used by some brands to compare deposit protection. This article is from 2016. Toyota, like Honda, found the test to be severely flawed due to the fact that it does not test used oil. Used oil has fuel contaminates in it. It is insolubles that are the main culprit of lower coking start temperature which cause deposit formation. Clean/new oil can be considered a value testing measure.

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Highlights of article:
Quote:
The Toyota team also conducted laboratory tests to look at when coking happens and under what conditions, evaluating both used oil and fresh oil. They found that key was the presence of insoluble materials, which in gasoline engine oils, were found to be polymerized hydrocarbons with carbonyl and ester functional groups. Lubricants with even small amounts of insolubles formed deposits relatively quickly at anything above 180o C. Those free of these external materials did not coke, even at significantly higher temperatures. For instance, fresh oil free of insolubles started to coke at 280o C, a full 100o C higher than used oils with insolubles in them.


Quote:
Since there was a big difference between the coking start temperatures with the used oil and the oil that was oxidised in-lab (coking temperature is well above 200° C), Toyota was able to determine that insolubles are the main driver of lower coking start temperature. Because the starting point is degraded fuel that’s been through combustion, fresh oil doesn’t exhibit anything like the temperature sensitivity and problem that used oil does.


Quote:
Toyota researchers also looked at screening tests to detect turbocharger coking, such as ASTM D6335, also known as the TEOST 33C test, which has been used in some of the ILSAC engine oil specifications. As already mentioned, the Toyota researchers found that the presence of insolubles derived from degraded fuel molecules was the key factor to reproduce the turbocharger coking phenomena. The TEOST 33C test does not involve it. Therefore, they do not think it is a good engine oil-screening test for turbocharger coking.


Deposit formation is not as simple as one may think. Over the years I've noticed via Amsoil's competitive oil testing, that Mobil 1 and a few other brands perform worse today on the TEOST test than they did back in the early 2000's. Currently, if you go to Mobil 1's website, they claim 2x better turbo performance than a competitive synthetic oil (regular Mobil 1) in turbo deposit protection. This was done using the Hot Tube Test as noted on their website. Now I understand why there is this discrepancy and also know what has more value in determining real world deposit protection.

Mobil 1 Hot Tube Test

Mobil 1 was head of the curve on turbo deposit prevention and LSPI. You're going back to 2006 and 2010.

One of the most important things an oil has to do in a turbo charged engine is not clean deposits, but prevent them in the first place.
 
Lets think of valve deposits on DI engines now concerning dirty gas diluted oil mist inhaled through the pcv.
 
Right. Take a look at JAG’s tests of oils that can dissolve deposits and clean varnish. Amsoil and Castrol performed very well. Mobil 1 didn’t appear to clean that well.
 
Wouldn't the same discoveries and same chemistry apply equally to ring coking problems, whether an engine is turbocharged or not?
 
Originally Posted By: buster
Right. Take a look at JAG’s tests of oils that can dissolve deposits and clean varnish. Amsoil and Castrol performed very well. Mobil 1 didn’t appear to clean that well.


And if any oil actually cleaned, every manufacturer would be selling it as the greatest thing ever. Even High Mileage oils don't claim to clean. Any benefits you "think" you are getting will be matched by any new oil you put in the sump. Even SonofJoe agrees that it's almost 100% chemically impossible for detergents to clean; they are there to keep the fresh contaminants suspended in oil until they can get to the filter. That's all... no magical cleaning abilities. You need a solvent for that, like Kreen, or MMO.
 
Any extra solvency/solubility beyond what is required by the target specifications of the product would be more or less a serendipitous consequence of chemistry IMO, not necessarily a feature. Because of this, product chemistry does change often and without notice; some more than others. So the suits wouldn't want to explicitly 'guarantee' cleaning powers in the market. That in mind, the most popular 'synthetic' hydrocarbon bases (III, IV) are 'dry' and exhibit low to no molecular polarity and that's very bad for solvency and solubility (cleaning). To add back that desired performance, various blendstocks and additives are used. Now this IMO is where the real differences are across the brands/blenders. Some of those additives are very costly. Some of them perform better than others. There is quite often a correlation between the cost and performance of these additives.
Therefore if extra-credit solvency and solubility happened to be in the product or not, it's ultimately controlled by arbitrary administrative and economic decisions IMO. Then you get products with wild variances in their (not officially qualified for) TEOST 33C test as we've seen. I'm sure there's something to be gleaned from the results.

Agree 100% about the usefulness of TEOST 33C
 
Very interesting, buster. Thanks. Those gasoline combustion by-products increase in concentration over the oil change interval, so the longer the OCI, I bet the increase in tendency to form turbocharger deposits.
 
Thanks for posting, buster.

The article mentions that the study looked at MoDTC, but it doesn't say what the findings are. I'd be interested to know. Anyone have any leads on that?
 
Originally Posted By: JAG
Very interesting, buster. Thanks. Those gasoline combustion by-products increase in concentration over the oil change interval, so the longer the OCI, I bet the increase in tendency to form turbocharger deposits.

Good point.

Maybe deposits around the top ring, too? Or do those involve sufficiently different mechanisms to be weakly related?
 
Originally Posted By: PeterPolyol
Any extra solvency/solubility beyond what is required by the target specifications of the product would be more or less a serendipitous consequence of chemistry IMO, not necessarily a feature. Because of this, product chemistry does change often and without notice; some more than others. So the suits wouldn't want to explicitly 'guarantee' cleaning powers in the market. That in mind, the most popular 'synthetic' hydrocarbon bases (III, IV) are 'dry' and exhibit low to no molecular polarity and that's very bad for solvency and solubility (cleaning). To add back that desired performance, various blendstocks and additives are used. Now this IMO is where the real differences are across the brands/blenders. Some of those additives are very costly. Some of them perform better than others. There is quite often a correlation between the cost and performance of these additives.
Therefore if extra-credit solvency and solubility happened to be in the product or not, it's ultimately controlled by arbitrary administrative and economic decisions IMO. Then you get products with wild variances in their (not officially qualified for) TEOST 33C test as we've seen. I'm sure there's something to be gleaned from the results.

Agree 100% about the usefulness of TEOST 33C


Great points.
 
Originally Posted By: d00df00d
Originally Posted By: JAG
Very interesting, buster. Thanks. Those gasoline combustion by-products increase in concentration over the oil change interval, so the longer the OCI, I bet the increase in tendency to form turbocharger deposits.

Good point.

Maybe deposits around the top ring, too? Or do those involve sufficiently different mechanisms to be weakly related?

I bet there is a strong relation. The oil in the ring pack is especially doused in combustion by-products. All areas inside an engine are like chemical reactors where the reactions are a function of the chemicals present, the temperature, the pressure, and the residence time. Conditions and chemicals are different in the turbo bearings than the ring pack, but I think there is enough similarity for there to be a strong relation between the deposits that develop in both areas. That is, I think that any changes made to the oil, fuel, or any other conditions that strongly affect the deposits in one area will usually strongly affect the deposits in the other area and in the same direction of better or worse. With complicated phenomena like this, I would not be surprised by some exceptions to that trend.
 
Originally Posted By: JAG
... I bet there is a strong relation. The oil in the ring pack is especially doused in combustion by-products. ... Conditions and chemicals are different in the turbo bearings than the ring pack, but I think there is enough similarity for there to be a strong relation between the deposits that develop in both areas. ...
That might be why there are two separate TEOST tests, run at different temperatures (aside from the defect of not testing with used oil).
 
Relevant thread from a couple of years ago (HT wemay): https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/4255864/Re:_Fuel_Economy,_MoDTC_and_TE

Apparently base oil composition has a big effect on deposit formation in this test, such that some base oil blends can keep TEOST deposits low even with a lot of MoDTC. FWIW.
 
I forgot earlier that MoDTC is one important example of an ingredient that can improve the performance in TEOST MHT and worsen performance in TEOST 33C.

Good find, dOOdfOOd.

I agree, CR94.
http://www.orbisbv.com/wp-content/uploads/2017/03/TEOST-Brochure-2017.pdf
Quote:
In the mid-1980’s, Savant Labs developed a unique two-stage oxidation/deposition test technique for engine oils formulated for high temperature performance. Joint cooperation with Chrysler Corpora- tion resulted in a modified, very high temperature cyclic technique successfully applied to oils blended for turbocharger lubrication temperatures. The technique, known as TEOST 33C, became ASTM D6335, and Savant Labs received a Chrysler Technology Award in 1993.
Additional work proved successful in modifying the TEOST to measure deposits on a thin- film of circulating oil. This lower, but constant temperature application, correlated to the piston ring belt area of the combustion engine. The TEOST MHT (Moderately High Temperature) protocol later became ASTM D7097. International engine oil specifications now include both the 33C and MHT tests.
 
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