camshaft lobe wear...

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This is a good find. Thanks for posting it. I don't want to read too much into this, but that said, I have been trying to make the point that camshaft wear typically doesn't show up in UOAs, and that it takes an experienced "operator" (pilot or motorist) to realize what's occurring as a result of oil shearing over time.
 
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This is what I thought too. Doing UOA without tearing the oil filter and weighing the metalic debris is basically useless. The thing is UOA are very easy to do and the oil labs are promoting it hard. This is the issue I currently have. Metallic Al flakes on the bottom of the oil pan, but great UOA results (Toyota's 2GR-FE engine).
 
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Hi, fuel tanker man - You said this; "Author says oil analysis won't always find cam lobe issues..." This is one reason that I have expressed caution in the analysis of "wear" from "simple" UOA results! A PQ Index reading and some other components in more sophisticated UOA Lab procedures helps - but tear down inspection is the only way to measure such things in components in real time use
 
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Hi, Steve S - Simple UOAs are a great tool for determining the condition of the lubricant - and for determining OCIs. One must be extremely careful in attributing wear metal uptake rates to various lubricants via such UOAs The new Boxster is a very good vehicle - perhaps one of the best vehicles ever made by Porsche. A Porsche in general terms is a better car to own than a Ferrari if you want to use it as intended - this especially applies to older versions of both marques!
 

fuel tanker man

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The pitting of the camshaft lobes is attributed, at least in some cases, to corrosion. (I'm drawing that conclusion based on the fact that such damage is said to be seen in engines which don't get a lot of use). Sticking valves are often the cause of cam lobe damage, the article says. I would think than in most automotive engines you would be able to notice a sticking valve, and you'd be having the valve train checked out asap... so you wouldn't need to rely on a UOA to show you cam lobe wear if a sticking valve was the cause... Then another major cause is not enough ZDDP in engines with high lift cams, which need the barrier additive to protect after the hydrodynamic film of oil is breached. Here is where the cam lobes would not come apart necessarily in chunks, but they would score (like in the 4 ball wear test) and put iron particles into the oil which would not be caught by the filter, and presumably show up in a UOA. The pitting lobes (indicated in the article linked) give off chunks of metal that the oil filter traps, but seemingly not a lot of tiny particulate matter that you'd find in the oil itself. Since we can't feasibly tear down an engine to assess how the lobes look, the UOA is better than nothing. We can at least see if indeed the lobe wear is in an advanced stage... or if the bearings are coming apart... if the UOA shows you that a cam lobe has reached the point that it is disintegrating, you can at least take the engine down then, rather than having something more catastrophic happen. Dan
 
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Hi, fuel tanker man - You said: "Then another major cause is not enough ZDDP in engines with high lift cams, which need the barrier additive to protect after the hydrodynamic film of oil is breached. Here is where the cam lobes would not come apart necessarily in chunks, but they would score (like in the 4 ball wear test) and put iron particles into the oil which would not be caught by the filter, and presumably show up in a UOA. The pitting lobes (indicated in the article linked) give off chunks of metal that the oil filter traps, but seemingly not a lot of tiny particulate matter that you'd find in the oil itself." In my quite considerable experience with accellerated cam lobe wear, there has been no evidence in UOAs. In many of these cases the causes have been poor metallurgy or hardening, or a ailure of a component that acts on the lobe (roller or roller spindle failure and etc) Corrosion in low use engines - especially those using lubricants with a low TBN - is a major if not the major case of cam lobe pitting. This does not always trash the camshaft (V8 928 Porsche engines is an example) but monitoring needs to be implemented
 

fuel tanker man

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Would that be because the chunks of cam material coming off the lobes are so large that the oil filter is trapping them all... but none are small enough to pass through the filter and show up in the UOA? Dan
 
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Hi, Dan - You are correct in a sense - A PQ Index reading may indicate some of the ferrous metal shed - as you know, UOAs measure content in PPM. In a simple explanation the oil pump's intake screen gets the big bits! These drop or may circulate outside the lubrication system in some cases. The typical FF filter will cover parts down to around 15microns @ around 50% and 5microns @ around 20-25% Depending on the type of Lab measuring devices used, results will vary. AA Spectrographic analysis is most sensitive to sub 5microns contaminants and may not detect those above 10microns Typically it is generally considered IMO that most cam wear (not corrosion) is caused by sub 2micron contaminants or those that may be greater in size than the the oil's film - an important component in consideration of the engines allowed minimum HTHS viscosity
 
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