Oil analysis "abnormal" readings

Ruh roh! I just got the analysis results back from my last oil change and the printout shows a couple of abnormal numbers, specifically, slightly high Aluminum (7 ppm) and Nickel (11 ppm). The comments section says "WEAR METALS APPEAR SLIGHTLY HIGH FOR OIL TIME, RESAMPLE NEXT OIL CHANGE TO CHECK WEAR TREND"

I figure that I'll fly it to another oil change and get another analysis done (obviously) to check the trends, but what components wearing will show high aluminum and nickel? The oil filter and sump screen were clean with no metal that I could see, engine has 685 hrs SMOH, cylinders are ECI Cerminil. Compressions are good and oil consumption is around 8-10 hrs/qt. I've had 7 previous reports with no problems, all done by AOA in Phoenix.

Should I be freaked out by this or just wait for the next oil change report?

Aluminum is usually from pistons, are your cylinders nickel plated?
It could be possible that you flew in dusty conditions, or taxi'd thru some dust with carb heat on? Carb heat bypasses the air filter, so dust could get right into the engine, put the hurt to your cylinders, pistons & rings, and while most of it ejects out the exhaust, some gets washed into the oil with the wear products in your report.
Also, how you take the sample effects the reading and the report accuracy varies somewhat as well.
When you put an engine into service, you have begun to wear it out. How fast it wears out is determined by how hard it's run, how dirty the intake air is, the oil change interval, how hot (or cold) it's run, chill shock on decent, excessive cold start-up, etc.
No two flights are the same, so some oil changes might reflect that dust storm you flew thru, or the cold yukon starts from an Alaska trip.
Make your choice and live with it.

SHIPCHIEF said:

... Carb heat bypasses the air filter, so dust could get right into the engine, put the hurt to your cylinders, pistons & rings, and while most of it ejects out the exhaust, some gets washed into the oil with the wear products in your report...

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It does? Is that something only on an -8?

The RV's (of recent vintage) I've worked on all had the carb heat entering the FAB in front of the filter, thus providing filtered carb heat.

N941WR said:

It does? Is that something only on an -8?

The RV's (of recent vintage) I've worked on all had the carb heat entering the FAB in front of the filter, thus providing filtered carb heat.

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No, the -8 is the same, carb heat air is filtered. I recall reading that dust and crud in the oil would elevate the silicon readings... but the alum and nickel values sounds like something expensive. Then again, maybe it's just an anomaly, I hope!

My advice to you is to file the oil analysis in the circular filing cabinet, and only pay attention to your screen and filter. I have seen oil analyses done on engines with known problems and they came back peachy with some friendly wording such as "nice wearing 540" when in fact the engine was self-destructing.

Statistical analysis

I'd love to see a statistical analysis on the measurement process. It's oil, and levels are at PPM. If you can, I'd send them a second sample of the exact same drain. See what happens then. Rick 90432

Your aluminum ppm is exactly in the range of where mine have been for almost 1200 hours. The nickel usually runs around 1 to 2 in my engine. These are normally 50 hobbs hour changes, with a quart added every 8 to 12 hours.

What were your numbers for the previous analyses?

I did get one bizarre analysis back a few years ago, and knowledgeable people told me it was likely a diesel engine oil analysis! Labs are run by normal people, so mistakes/contaminations happen.

the key word here is TREND. 1 sample can be high or low, but trend will track.

One important to do:

Always take the sample under the same conditions using the same method.

AlexPeterson said:

What were your numbers for the previous analyses?

I did get one bizarre analysis back a few years ago, and knowledgeable people told me it was likely a diesel engine oil analysis! Labs are run by normal people, so mistakes/contaminations happen.

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I usually change my oil between 40-50 hours and always take the sample using the same technique. Trends have been okay, but now there's a jump... I'm hoping for a goof or anomaly. I'd call them directly but too expensive to call from Bogota, Columbia...


Here's the printout with trends, it's somewhat readable.

Elevated levels of aluminum for non turbocharged engines is above 30 parts per million according to lycoming.

this looks like nothing to worry about on the aluminum. The nickel seems high, but I am not sure, nor can I find a reference for a cautionary limit. I might consider pulling the filter and sucstion screen and taking a good look.

It is my understanding that high nickel can indicate valve guide wear.

Sometimes too much knowledge is bad!

When I had my inspection last year for my Airworthiness Certificate on my RV-4FB, the 'old school' DAR (over 1,00 AWs issued) was chiding me on all my gadgetry in the cockpit, ie EFIS, EGT/CHT in all cylinders, etc. "All that stuff will just make you nervous! These engines ran fine without them!" He explained Lycomings have been installed in aircraft for years and really, even with all the modern engine monitoring systems we have, the average life spans of our engines have remained about the same, with or without monitoring, or engine oil analysis. I guess my point is: Monitor, but trust. It's probably all right!

One more thing, in the USAF all jet engines get SOAP/JOAP oil analysis on a very regular basis. In general, and as indicated by an earlier post, they are not of much value until there is a LOT of metal in the analysis, and by that time it was evident to the dullest amongst us that the engine was toast. So again, "All that stuff will just make you nervous!" It's probably all right.

Jconard said:

It is my understanding that high nickel can indicate valve guide wear.

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Well huh, I think I know where that's coming from then. The #2 cylinder exhaust valve... it stuck a few months back and the shop that popped it loose said the valve guide had just a wee bit of play in there and gotta keep an eye on it.

I guess I'll see what the next analysis has to say...

Al normal, nickel high

I have access to a spectometer and have been doing oil analysis for a friend for several years, since his engine was new--from 2002 to 2009 and he has over 1000 hours now. Been doing it for some others, but he is the only one submitting samples regularly for a Lycoming.

Aluminum for the last 5 changes averaged 4.7 ppm. Yours is slightly higher--what was it last time?

Nickel averaged 0.9 ppm for same time. Obviously yours is a lot higher, but I didn't need to tell you that.

As others have said, it's the trend that counts. And as the lab said, resample at the next change. If you still have the oil you drained out, you could resample it, but it could have gotten contaminated when it was drained and it might all be contaminated. Contamination is easy to do. Some of the guys at the lab used to demonstrate how sensitive the machine is and how easy it is to contaminate a sample by rubbing a penny with their fingers, then running a little oil over their fingers and run that thru the spectrometer. There would be several ppm more in the sample exposed to penny rubbing than to uncontaminated oil. It didn't take much rubbing. Crew chiefs had a problem for awhile with not cleaning off the sample tube before taking a sample. We would frequently have to send them back to resample. They learned.

Nickel has a lot of uses--stainless steel and other alloys, batteries, coinage, magnets, etc.--it would be easy to contaminate a sample. Hopefully, that's what happened.

John,

I routinely deal with analytical data (on rocks, not usually engines) but typically there is a lot of uncertainty in the data at ppm levels. I would be interested to see what the +/- is on these analyses. My guess (and fur certain it is a guess since I don't have any real experience with the analytical end of oil analysis) is that for most of these elements at those levels, the uncertainties would make most of these numbers almost the same. At the ppm level, it's easy to get some contamination as well. I wouldn't worry about it unless it keeps going higher. Also, as someone mentioned, it would be interesting to run multiple aliquots of the same oil at the same lab for comparison (and would also be interesting to run them at different labs for comparison!).

cheers,
greg

Jconard said:

Elevated levels of aluminum for non turbocharged engines is above 30 parts per million according to lycoming.

this looks like nothing to worry about on the aluminum. The nickel seems high, but I am not sure, nor can I find a reference for a cautionary limit. I might consider pulling the filter and sucstion screen and taking a good look.

It is my understanding that high nickel can indicate valve guide wear.

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I use these:

Item Abnormal Severe

Iron 130 ppm 240 ppm
Alum 30 ppm 55 ppm
Chrome 24 ppm 48 ppm
Copper 30 ppm 60 ppm
Silicon 18 ppm 60 ppm
Tin 36 ppm 72 ppm
Nickel 18 ppm 36 ppm

It takes three samples to make a trend in my book. Chrome levels will be allowed higher with chrome cylinders to 48 as abnormal and 96 as severe.
Good Luck,
Mahlon
“The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."

The spectrometers the USAF uses vary about 2 ppm just in measurement errors, but a few elements vary more than others--not nickel, iron or aluminum, however. Other spectrometers may or may not vary more.

And despite what another said, we saved several engines with OA and it easily paid for the program. You don't want to lose an engine in an F-16 50 miles offshore. The AF varies the OA requirement for each aircraft based on a statistical history of each type combined with it's configuration and it's mission. F-15's get checked after the first flight of each day; tankers with 4 engines are on a different schedule, if they are checked at all.

You have to keep in mind that oil filters and magnetic plugs aren't looking at the same things. You can get an OA hit and have it not show in the filter and be valid and you can see metal in the filter and not in the oil sample and it can be valid, too. The particle size is the difference--OA sees sizes of a few microns, filters, well you can see those particles.

Lastly, there is operator error or carelessness. One of our guys deployed for a NATO exercise and ran into a gal we had met in Saudi Arabia. We had noted that she was just putting in her time and didn't give a hoot. She brought the spectrometer from her home unit that deployed units were supposed to share on this mission. Our guy asked if it had been standardized, which takes an hour or two and one must do whenever the machine is moved. "Oh, sure, it's all done." she said. Then he noted that the machine hadn't even been plugged in. She had just planned to turn it on, to a daily calibration and go. And her unit has single engine F-16's.

I noticed one of the replys metioned oil change intervals at 50 hrs on the hobbs meter. I guess I assumed tach time would be more relevant as it is actual engine run time (above 1500 rpm on mine) and would not take into account idling time or when the master switch was on and the engine was not (unless you have an oil pressure activated hobbs). Is it common practice to use the hobbs meter or tach time?

hea tim,

hows she flying? i do 25 hr cycle on oil changes. using the hobbs that puts me at 30 hr hobbs intervals. oil sample at 30, then oil filter at 60. at 30 i can get the hose hooked up to the quick drain thru the oil door. this makes it easy to do on trips when away from home. love clean oil. turbo