oil analysis follow-up

[Matt C]

I posted a while asking for oil analysis lab suggestions. I sent samples from my first oil change on this plane to AvLab and Blackstone. I also sent the oil filter to AvLab. There was approximately 25 hours on the oil and filter. They sent results that were dramatically different. The samples were collected almost simultaneously. I drained a quart or so, collected both samples and then drained the rest without pausing during the draining process. I don't recall which was collected first (dang it). In parts per million the results are as follows with the AvLab result first -

iron 31.6 - 123
aluminum 4.4 - 20
lead 1143 - 2611
silicon 12.5 - 4
chromium 0.4 - 2
copper 5.9 - 7

I know the real interest is in establishing a trend, but I'm also surprised at the significant differences. One indicates fairly normal (or "expected" or "average") results and the other indicates (sort of) potential trouble to watch for.

BTW, the oil filter sample indicated trace amount of aluminum flakes 1059x711 microns to 27x18 microns. "This alloy is commonly used in piston pin caps and plugs" was the comment. No other notations from the filter....

Curious about feedback from you all.

Regards

 

[coloradobluesky]

Your oil filter is collecting some metal. I don't know, maybe they all do that. What is the compression on the engine and is it making Top Speed and burning fuel normally? Usually they analyze the oil filter by seeing the particles visually.

Never heard of anyone doing what you are doing. Comparing oil filter oil with crankcase oil. I suggest dont do that and instead have an experienced mechanic visually inspect the oil filter to see if the metal is collecting there normally. The oil filters Ive seen have little hard specs of carbon, and nothing else visually apparent.

Thats the problem with oil analysis. No one really knows what the readings mean. Unless limits are specified by the engine mfg and they arent for Lycomings and Conts that I have ever seen.

 

[mtuomi]

I don't think OP is comparing oil filter oil to crankcase oil - he just said he also sent the filter to AvLabs.

 

[GRG55]

I am a bit of a heretic. I take the same approach with my planes as I do with my businesses - I only collect data that is useful to improve how I run them.

Despite the many testimonials I have heard from fellow owners at our airport cafe over Saturday breakfasts, I have never actually figured out what I would do differently with the information from oil analysis labs.

Let's suppose one has a fairly constant trend for some time and then one or two elements trend up. What would you do, especially if there is no other indication of a problem? One cannot shorten the time interval for the next sample because the results are then no longer comparable. So likely run it the same time and see if It repeats? What if it's higher still? I'm genuinely curious about the decision process those who use oil analysis would expect to employ, if they actually get the results they are hoping not to?

Me? I change my own oil and inspect my own filters. And I think the physical evidence in a filter would almost certainly be necessary for me to consider tearing down a bottom end prematurely. Cylinders give lots of other indications as they start to go bad.

 

[James331]

I'm not really into that stuff.

I cut my filter and also know where my plane like to run, "in the green" isn't good enough.

 

[Goofy]

Blackstone will give you excellent advice and probably did so on your report. Call them with any questions. Have heard good of some lousy experiences with the AV guys despite, what I understand is, a relationship with Mike Busch.

 

[denverpilot]

We've always done it. Blackstone. They caught that we had a hole that was a little flap you couldn't see easily, in our air filter. Higher silicon.

We also cut open our own filters and peruse the pleats for things we hope not to find.