Do UOAs give a hint that sludge is forming?

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Jan 18, 2003
I've noticed some people on here are going 7500 and 10,000 mile on OCI with dino oil. With what looks like good results. But I got to wonder if UOAs are telling the whole picture. Is it possible that sludge is forming and the UOAs are not telling entire the story? TIA
The UOAs tell the shape that the oil is in plus what mechanical shape that the engine is in along with how it is wearing. Unless the sludge was so bad that it was actually circulating in the oil I doubt it would show in the sample.
Normal metal spectro do not but run a IR and you can see spikes in a cetain range the corrolate to "sludge" or oxidized stuff.

IR or FTIR runs about $50 more and they may want a Virgin oil for a baseline.

Do you actually need to "step up" to IR/FTIR? Wouldn't a TBN and insolubles, together with a careful look down the oil filler (assuming a meaningful view, which some engines don't provide), give you at least 90% of what you want to know? If you have low insolubles, and a stable, safe TBN, where could sludge come from in the first place?

You have to answer within ten minutes, or I'll ask you more questions about Synlube!
I don't have the threads handy, but do recall that people in this forum ending with sludge in spite of good UOAs. As previously mentioned an FTIR seems to be needed to reliably detect sludging in a UOA.
insolubles and tbn depletion are sometimes like a engine oil idiot light in that when the tbn drops and the insoluble go up yop already have sludge forming and sticking to the engine surface that is why insolubles are OK but not the final answer.
IR will show the beginning better.

Synlube **** do not ruin my day

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