Engine Oil Formulations for Improved Deposit Control

[JAG]

http://oil-additives.evonik.com/sites/lists/RE/DocumentsOA/stle-2016-deposits.pdf

They showed interesting results. I wish the slides had more and better text. I’ll will do my best to summarize them.

TEOST 33C Deposits when base oils (apparently without additives) ranged from Groups I to III+ showed low amounts of deposits with no consistent trend of improving or worsening as Group # increased. If there really were no additives, then these and later results indicate that the additive packages they later used significantly increased the amount of deposits.

“DI” package is abbreviation “detergent inhibitor” package, often meaning most or all of the additive package. Not surprisingly, the package itself as well as the treatment rate affected the amount of TEOST 33C deposits. A certain DI at recommended treat rate in Group II base oil outperformed two other DI packages in Group II/III blends.

In my opinion, the authors botched determining the effect of molybdenum concentration on deposits because they didn’t vary it while keeping everything else constant. They also varied base oil type and DI package type and treat rate. Because of that, I’m not going to mention what those results were.

Viscosity modifier (index improver) type affected deposits, as did its treat rate, with increasing treat rate increasing deposits.

In contrast to the apparently additive-free base oil results, with a certain DI package, Group III+ made significantly less deposits than Group II/III blend did.

They showed results with various fluidizers added. I’ve never heard of a fluidizer before in lubricant literature.

Adding high molecular weight weight PAO 40 (40 cSt at 100 C) and adjusting the viscosity modifier treat rate to maintain the HTHS viscosity significantly decreased deposits when used at 2.5 to 10% treat rate. The improvement nearly leveled off at 5% treat rate. The improvement was large enough to drop the deposits from a terrible amount to easily passing even though a large amount of molybdenum (500 PPM) in the form of MoDTC was present.

VW TDI test’s piston deposits did not correlate well with TEOST 33C deposits.

Microcoker deposits did show promise as a predictor of VW TDI deposits.

 

[d00df00d]

Very interesting! Thanks for posting.

Originally Posted By: JAG
TEOST 33C Deposits when base oils (apparently without additives) ranged from Groups I to III+ showed low amounts of deposits with no consistent trend of improving or worsening as Group # increased. If there really were no additives, then these and later results indicate that the additive packages they later used significantly increased the amount of deposits.

I wish more people understood this. If they did, I bet there'd be a lot less enthusiasm for certain "boutique" oil blenders with everything-but-the-kitchen-sink add packs.


Originally Posted By: JAG
In my opinion, the authors botched determining the effect of molybdenum concentration on deposits because they didn’t vary it while keeping everything else constant. They also varied base oil type and DI package type and treat rate. Because of that, I’m not going to mention what those results were.

I bet there was a reason for this. It seems like a pretty rookie mistake otherwise. Could it be that they focused on certain typical kinds of formulations because not all combos of base oils, DI packages, and moly concentrations work well enough to be worth considering?


Originally Posted By: JAG
VW TDI test’s piston deposits did not correlate well with TEOST 33C deposits.

This isn't hugely surprising, but it is interesting -- and a good reminder that not all "deposits" are created equal.

 

[JAG]

Yeah, there could be a good explanation for why their showing the MoDTC effect was valid. The text just doesn’t explain it.

Yes, deposits are very complicated. For example, MoDTC increases deposits in the TEOST 33C test and decreases them in the TEOST MHT test. In the former, carbide (from MoDTC) deposits are created and in the MHT test, MoDTC’s antioxidancy reduces oxidation thereby reducing deposits. The conditions to create carbide deposits simply aren’t present in the MHT test.

 

[JAG]

I found another paper.
https://www.savantgroup.com/media/2010-P...EOST33C-TAE.pdf

One thing that was found was that API SA oils, lacking additives, performed extremely well in the TEOST 33C test. Clearly, additives generally increase deposits.

There is a lot of variation in results in fully formulated oils. Results have changed somewhat over the last two decades. Also results for oils made in different regions of the world perform differently.

No correlation was found between amount of deposits in TEOST 33C and TEOST MHT.

 

[CR94]

Originally Posted By: JAG
... No correlation was found between amount of deposits in TEOST 33C and TEOST MHT.
Interesting! What does correlate with the TEOST MHT results? Is 0w-20 exempted from that one too? It's more interesting to me (and I'd hope a lot of other people) than 33C, for reasons probably obvious.

 

[JAG]

0W-20 is not exempted.

Here is what I found that didn’t require paying for a paper. I’ll look for more this evening.
https://www.tannasking.com/documents/15/TEOST_Brochure.pdf

“In the mid-1990s, Savant Laboratories researched and produced a bench test for piston deposits. Correlation was shown between the TEOST MHTTM method and the Peugeot TU3MH engine varnish test (R-squared >= 0.90). This resulted in a required OEM standard for specifying engine oils.”

 

[CR94]

Thanks, JAG! I'd suppose ring coking knocks out at least as many engines as turbo bearing coking. That could change, with turbochargers becoming more common.