Engine oil additives little changed during OCI

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Originally Posted By: CT8
The additive change little by measurement but they can be depleted.
Do you mean (for example) that Zinc (ZDDP) and Moly numbers remain high, but "insolubles" get so high that they negate the remaining additives?
 

CT8

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The calcium for example will still to spec but it wont buffer any more.Looking at the UOAs the additive PPM numbers seem not to change
 
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For big diesel engine they publish guides as to when to change. Iron, soot, fuel dillution, and TBN. When one of them gets too high or low its time to change the oil. The ppm of additives is not really directly considered.
 
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You may see additive elements (Zn, P, Ca, Mg etc) actually increase over time due to concentration by volatility - as the lighter base oil fractions evaporate they leave behind the additives. Some of the detergent elements can be caught in the filter - for example CaCO3 (the 'B' in TBN) reacts with sulfuric acid (from combustion of sulfur-containing fuel) and a bit of water to become CaSO4, aka plaster of Paris - this oil-insoluble salt then gathers in the filter, hence removing Ca from the oil. It's a small effect though and may not be noticeable, especially with the volatility effect described above.
 

MolaKule

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Quote:
You may see additive elements (Zn, P, Ca, Mg etc) actually increase over time due to concentration by volatility - as the lighter base oil fractions evaporate they leave behind the additives.
If an additive component contains say an initial 80 ppm of MoDTC, where would the xtra moly come from even if some of the lighter base oil fractions were to evaporate?
 
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How are "additive levels" being measured? An ICP analysis will show the same elements regardless of the ability of any additive to be chemically effective.
 
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Originally Posted By: MolaKule
Quote:
You may see additive elements (Zn, P, Ca, Mg etc) actually increase over time due to concentration by volatility - as the lighter base oil fractions evaporate they leave behind the additives.
If an additive component contains say an initial 80 ppm of MoDTC, where would the xtra moly come from even if some of the lighter base oil fractions were to evaporate?
The overall concentration would increase as the diluent (base oil) was lost. If you have 80 ppm MoDTC in a sump containing 5000 grams of oil and say it were 15% volatile. The loss of that 15% would leave you with 4250 grams of oil. With a concentration of 80 ppm, you would have had 4 grams of MoDTC in the original volume. That same 4 grams of MoDTC now in 4250 grams of oil would result in a concentration of 94 ppm.
 

MolaKule

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You're assuming a fraction of the 80 ppm MoDTC will not leave with the 15% volume of the oil that was lost. I don't think conservation of mass supports your theory.
 
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Originally Posted By: MotoTribologist
Originally Posted By: MolaKule
Quote:
You may see additive elements (Zn, P, Ca, Mg etc) actually increase over time due to concentration by volatility - as the lighter base oil fractions evaporate they leave behind the additives.
If an additive component contains say an initial 80 ppm of MoDTC, where would the xtra moly come from even if some of the lighter base oil fractions were to evaporate?
The overall concentration would increase as the diluent (base oil) was lost. If you have 80 ppm MoDTC in a sump containing 5000 grams of oil and say it were 15% volatile. The loss of that 15% would leave you with 4250 grams of oil. With a concentration of 80 ppm, you would have had 4 grams of MoDTC in the original volume. That same 4 grams of MoDTC now in 4250 grams of oil would result in a concentration of 94 ppm.
You're absolutely 100% correct. I used to see this all the time on the Sequence IIIG and Peugeot TU5, especially on high Noack oils. It used to amaze me how many of my fellow formulators could not get their heads around something that to me was so blinding obvious.
 
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Originally Posted By: SonofJoe
Originally Posted By: MotoTribologist
Originally Posted By: MolaKule
Quote:
You may see additive elements (Zn, P, Ca, Mg etc) actually increase over time due to concentration by volatility - as the lighter base oil fractions evaporate they leave behind the additives.
If an additive component contains say an initial 80 ppm of MoDTC, where would the xtra moly come from even if some of the lighter base oil fractions were to evaporate?
The overall concentration would increase as the diluent (base oil) was lost. If you have 80 ppm MoDTC in a sump containing 5000 grams of oil and say it were 15% volatile. The loss of that 15% would leave you with 4250 grams of oil. With a concentration of 80 ppm, you would have had 4 grams of MoDTC in the original volume. That same 4 grams of MoDTC now in 4250 grams of oil would result in a concentration of 94 ppm.
You're absolutely 100% correct. I used to see this all the time on the Sequence IIIG and Peugeot TU5, especially on high Noack oils. It used to amaze me how many of my fellow formulators could not get their heads around something that to me was so blinding obvious.
Seems just like harvesting salt by letting seawater evaporate...
 
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Originally Posted By: MolaKule
You're assuming a fraction of the 80 ppm MoDTC will not leave with the 15% volume of the oil that was lost. I don't think conservation of mass supports your theory.
You are 100% correct in the assumptions made but it was just mena to be a simple answer to your question. I've never thought about this topic before this time though. Vaporization of the base fluid would likely carry away some of the MoDTC solubilized within as you say. However isn't it also likely that as the oil vaporizes it's decreased density would force a lower concentration of additives in that portion than the liquid portion no? Maybe I am just thinking myself into circles but that makes sense to me sans any evidence or actual research. Edit: Plus, conservation of mass assumes a closed system (even if that system is the entire universe in most cases). This question is in regards to the engine oil as the system and it being open to the environment so there can certainly be net changes in mass.
 
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Distillation can be unpredictable. Any non-volatile components in the mixture will not appear in the distillate but anything that has a similar boiling point to the hydrocarbon fractions of the oil will carry over. Are the additives liquids or are they solid compounds dissolved in a hydrocarbon carrier? I don't know enough about formulated motor oils to answer that. Plus it isn't a closed system for more reason than one.
 
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Originally Posted By: Virtus_Probi
Seems just like harvesting salt by letting seawater evaporate...
Yes sort of but sodium chloride is an ionic compound that doesn't carry over into the distillate. Is that how it is with additives in oil?
 
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Originally Posted By: kschachn
Originally Posted By: Virtus_Probi
Seems just like harvesting salt by letting seawater evaporate...
Yes sort of but sodium chloride is an ionic compound that doesn't carry over into the distillate. Is that how it is with additives in oil?
I've shockingly never questioned the pure form of MoDTC before. According to a few sources that may or may not be accurate, it is a yellow powder only soluble in phosphate esters and diester fluids. MoDTC1 MoDTC2 MoDTC3 So I guess the possibilities are either the dissolved MoDTC is carried away as part of the mixture or it would dissociate from the vaporized fluid and reenter the liquid thereby increasing the overall concentration. Again, I have absolutely no idea how factual that is, just spinning the wheels happy
 
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Most commercial organic molys are thick, black, gungy semi-liquids. Like most additives, at typical engine oil temperatures, they are essentially non-volatile.
 
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Originally Posted By: SonofJoe
Most commercial organic molys are thick, black, gungy semi-liquids. Like most additives, at typical engine oil temperatures, they are essentially non-volatile.
Does a by-pass filter filter them out?
 

MolaKule

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As I explained in another thread, most modern organo-metallic AW and FM additives are liquids so as to be oil soluble:
Quote:
There are processes for preparing the organo-metal compounds which involves converting an alkali metal dihydrate of a Group VI metal; e.g., sodium metal dihydrate, to the corresponding metal acid hydrate of the Group VI metal. The metal acid hydrate is then reacted with an alkyl amine to form the organo-metal compound. This can be done with Molybdenum, Titanium, Tungsten, Antimony, or just about any other metal.
 
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