pH instead of TBN/TAN

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This article piqued my interest, and pH is traditionally only an aqueous solution, and a measurement of the "free hydrogen" (proton) content of an aqueous solution...so doing a pH test on oil made me alert.

http://www.machinerylubrication.com/Read/100/ph-test-tan-tbn

Note not just the article, talking about making use of the "TAN" solution, which is cosolving the oil with toluene, IPA, and water in specific ratios...can't get it to work without water, and can't dissolve the oil without co-solvents.

The article is interesting, but then the comments from a reader, and the response are amazing (IMO).
 
I honestly thought about this concept a couple of months ago. I wondered if one could test used oils ph value at home. Also this could be performed with coolant has well. But I figured that a simple buffer strip would not be as accurate within tolerances that truly provide accurate enough feedback to do any good.
I found it interesting in the last response that the fellow said that there was too much correlation that the ph testing they were performing had validity. I would agree with this assertion because of the fact of reproducibility of results.
Now in terms of a machine that could actually perform a ph test at home that could be relevant, accuate, and reproducible is the cost involved. It would likely price to be cost prohibitive for most people to invest in one to be worth purchasing. I would assume a business with a fleet of vehicles may well be able to justify the cost of such a machine over a long run period of time.
 
OK Friday evening update. End of an extraordinarily hard week, so fun time.

Ordered a pH meter off ebay. Bought some xylene (toluene is some drug lab ingredient, so unobtanium unless I start pulling apart some MSDS'), IPA, and a couple of syringes.

Into the bowl end of an upturned beer can (It's Friday), I put 3ml of bottled water, 3ml of IPA, and 3ml of xylene.

They sort of co-solved.

Then added 3ml of used engine oil (my 5W40 frankenbrew multiple synthetic that I ditched at 5,000km, but keep a sample of in the freezer).

Used engine oil sat for a bit, then little "worms" of it started scooting off all over the place. Used a syringe to circulate the lot, and make an emulsion, over a couple of minutes.

pH probe showed 7.8.
 
OK, did the oils in the Stash this afternoon. Same drill, 3ml of oil, 3ml xylene, 3ml IPA, 3ml waer.

Castrol Edge 5W30 A3/B4, pH 8.7, advertised TBN 10.2
Mobil 1 5W50, pH 8.1, advertised TBN 11.8
Chief 5W30 syn A3/B4, pH 8.9, advertised TBN 9.7 (going in the Caprice next time)
Penrite SAE30 small engine, pH 9, no advertised TBN
Castrol Magnatec SP 5W40, pH 8.7, no advertised TBN (currently 5,000km into OCI on the Caprice)
 
What's the pH of just the solvent mixture, no oil? I'm curious if some of that "retained TBN" is the solvent signature the article mentions.

Ed
 
Good call, will have a look tomorrow, it's gone dark, and freezing.

as an aside, the mix is much more stable with used oil than new.
 
Because used oil looses surface tension and mix with water, mostly because of emulsification already done by its running.
 
I take it you haven't read the threads where siloxane polymers are used to reduce oil bubble surface tension.
 
Actually, I havent
smile.gif

I know ... silicone additives, group V to reduce bubbles. Why do you ask that?
Old oil mix better with water is the fact, not silicone additives. Are you picking on my foot, eh?

Ok I may have confused with oil beading up better when new ? Not a surface tension case ... (?)
wink.gif
 
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The system of calcium sulfonate/sulfonic acid is that of a weak base/weak acid. That is to say, it is buffered. Therefore pH won't change much until almost all the Ca sulfonate (or phenate or salicylate) is used up (turned into weak acid). Therefore to figure out TBN a titration must be done, which is precisely the methodology used already.
The pH methodology in the article determines only when the base in the oil is already used up; it isn't capable of telling how far one has to go to get to that point.
I suppose a combination pH/TBN/TAN assay would tell a person which criterion is best for condemnation. E.g. Blackstone's TBN>1.0; the TBN/TAN "crossover" point; or TBN = 1/3 VOA TBN.

Charlie
 
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