Oil Analysis on M20K during purchase

[MooneyAcolyte]

Dear all,

while trying to close in on a deal to buy a M20K, I got a bad surprise when the oil analysis came back from the pre-buy. The engine is only 600 hours and the filter check was clean, but from the oil analysis I get:

Iron: 145 ppm

Copper: 20 ppm

Chrome: 40 ppm

Aluminium: 13 ppm

Nickel: 52 ppm

all other values are in the green. I'm still interested in the aircraft and am wondering if this could simply be a case of "old oil" or is it really a concern? What could be the source? Any advise from more knowledgeable people than myself? Any help is appreciated.

[cferr59]

When was it last changed and how many hours were on it?

[anthonydesmet]

Would also help to know the reference numbers of each categories for that engine.  Were any of those numbers an abnormal spike from previous analysis and then if so had the aircraft been sitting for months, last time the oil was changed, how many hours flown since last, average hours in last month, how much oil is it using etc.

oil analysis is only a small part of painting the overall health of the engine.

how was the compression test? How was the test done? Borescope?

[M20R]

I just got my oil analysis and the values are:

Iron:   16

Copper:  5

Chrome:  2

Alumin.: 5

Nickel: 0

The engine has 1300 hours and has never been apart.

[milotron]

My last testing on my MB M20K:

Iron:   63

Copper:  4

Chrome:  8

Alumin.: 12

Nickel: 18

 

1550 hours with bottom end IRAN at 1300.

[GeeBee]

Without context, i.e. how much time in hours and calendar on the oil, even the sampling method, what previous reading were etc it is difficult to make any conclusions

[carusoam]

When it comes to oil analysis, context is everything...

How many hours the oil was in use...  those same numbers go from very low to very high....

How the oil got sampled...  hot after a flight, caught as the oil drains, is most representative...

 

Using a single oil analysis without any context is similar to cylinder compressions... except, to retest requires running more oil through the engine for 25hrs or whatever the number of hours was used with the comparative samples...

Of course, if those ppm were measured in millimeters you can read the part numbers on them to know what part they were associated with...

using engine oil analysis for a purchase decision probably isn’t very helpful to anyone without a chemistry degree, or the owner of the plane...

The good news, there was no report of metal flakes in the oil screen....?

PP thoughts only, not a mechanic...

Best regards,

-a-

[LANCECASPER]

9 hours ago, wannabeMooniac said:

Dear all,

while trying to close in on a deal to buy a M20K, I got a bad surprise when the oil analysis came back from the pre-buy. The engine is only 600 hours and the filter check was clean, but from the oil analysis I get:

Iron: 145 ppm

Copper: 20 ppm

Chrome: 40 ppm

Aluminium: 13 ppm

Nickel: 52 ppm

all other values are in the green. I'm still interested in the aircraft and am wondering if this could simply be a case of "old oil" or is it really a concern? What could be the source? Any advise from more knowledgeable people than myself? Any help is appreciated.

Had the owner done oil analysis? What would be valuable is to see what the last few have been.

[kortopates]

The value of oil analysis is strictly limited to trend analysis. I wouldn’t conclude anything on a single sample in isolation. Far far more important is looking at the oil filter and oil screen.


Sent from my iPhone using Tapatalk

[M20F]

6 hours ago, GeeBee said:

Without context, i.e. how much time in hours and calendar on the oil, even the sampling method, what previous reading were etc it is difficult to make any conclusions

+ Kortopates comment, it’s a trend not an exacting science.  At 1300hrs one should expect best case to have to take apart within the next 5yrs, worst case 5 minutes after you buy it.  
 

You really have no engine predictability until you overhaul and monitor yourself, everything else is just WAG.  

[MooneyAcolyte]

On 11/7/2020 at 12:37 PM, cferr59 said:

When was it last changed and how many hours were on it?

Owner said it was changed 30 hours ago and the engine has 600 hours since overhaul 13 years ago

[MooneyAcolyte]

On 11/7/2020 at 4:13 PM, M20R said:

I just got my oil analysis and the values are:

Iron:   16

Copper:  5

Chrome:  2

Alumin.: 5

Nickel: 0

The engine has 1300 hours and has never been apart.

Thanks much - hmm. Looks like there is something going on in that engine ... Yours looks super!

[MooneyAcolyte]

On 11/7/2020 at 1:31 PM, anthonydesmet said:

Would also help to know the reference numbers of each categories for that engine.  Were any of those numbers an abnormal spike from previous analysis and then if so had the aircraft been sitting for months, last time the oil was changed, how many hours flown since last, average hours in last month, how much oil is it using etc.

oil analysis is only a small part of painting the overall health of the engine.

how was the compression test? How was the test done? Borescope?

Our friend's @M20R numbers above look quite right. The compression test was okay, all above 70, except #3 was 61 - after some fidgeting. Might be that.We did a borescope, but unfortunately the equipment my mechanic brought was not great and we could not see anything. Thanks for the suggestion.

[MooneyAcolyte]

21 hours ago, LANCECASPER said:

Had the owner done oil analysis? What would be valuable is to see what the last few have been.

Good idea! I'll ask him to send me another one after an oil change and 10 hours.

[MooneyAcolyte]

On 11/7/2020 at 6:03 PM, carusoam said:

When it comes to oil analysis, context is everything...

How many hours the oil was in use...  those same numbers go from very low to very high....

How the oil got sampled...  hot after a flight, caught as the oil drains, is most representative...

 

Using a single oil analysis without any context is similar to cylinder compressions... except, to retest requires running more oil through the engine for 25hrs or whatever the number of hours was used with the comparative samples...

Of course, if those ppm were measured in millimeters you can read the part numbers on them to know what part they were associated with...

using engine oil analysis for a purchase decision probably isn’t very helpful to anyone without a chemistry degree, or the owner of the plane...

The good news, there was no report of metal flakes in the oil screen....?

PP thoughts only, not a mechanic...

Best regards,

-a-

I'll ask for another analysis and make sure it is taken properly. Thanks for the suggestion.

[carusoam]

1 hour ago, wannabeMooniac said:

I'll ask for another analysis and make sure it is taken properly. Thanks for the suggestion.

wanna,

I think you are missing a small detail here...

1) Hopefully, the owner has been doing oil analysis all along...

2) If he did it at 50hr intervals.... you can compare a new oil sample to the previous oil samples...

3) New oil has 0ppm of metals in it....

4) To get comparable numbers... you have to run the engine 50hours in a similar way...

 

5) The bad news... the chance of getting a Comparable sample is pretty slim without waiting a few months...

6) The good news... a plane with real metal problems... the numbers go so far off the scale, you aren’t seeing real metal problems with what you have...

7) If a plane is flying regularly... it has little chance of letting its cam and lifters croak...

8) If a plane is sitting idle... this type of oil analysis will give all kinds of erratic numbers...

9) Flying regularly, is good...

10) Not flying can be terrible, or not bad at all...

11) You will have better odds by looking at a cam follower or cam lobe...

12) But, by the time you have seen them all... you have just completed the effort of a top OH...

Buying a pre-flown plane can be a dice roll... or else they would cost the same as a new plane...

Minimize your risk wisely...   oil analysis done this way, is going to reject a lot of engines...

Hopefully this is helpful to put some context of what you are trying to do, with how good oil analysis really is...

PP thoughts only, not chem lab professor...

Best regards,

-a-

[milotron]

1 hour ago, wannabeMooniac said:

Our friend's @M20R numbers above look quite right. The compression test was okay, all above 70, except #3 was 61 - after some fidgeting. Might be that.We did a borescope, but unfortunately the equipment my mechanic brought was not great and we could not see anything. Thanks for the suggestion.

Remember that the M20R is non-turbo. The turbo is hard on oil and samples will reflect this. Comparing analyses between different engines will be less helpful.

 

the blackstone analysis should have 'normal' values derived from their sample data and that is a reasonable comparison over time.

[LANCECASPER]

4 hours ago, wannabeMooniac said:

Good idea! I'll ask him to send me another one after an oil change and 10 hours.

In today's market, if that airplane is a good value it will be gone by then. If the rest of the pre-buy looks good, buy it. If you're in search of the perfect airplane, your search will be endless.

[cferr59]

4 hours ago, wannabeMooniac said:

Owner said it was changed 30 hours ago and the engine has 600 hours since overhaul 13 years ago

Sorry, I wasn't clear.  I was wondering how much calendar time is on the oil.  For example, if it was changed in 11/2019 and has 30 hours on it, it was sitting a lot and you would might expect to see high iron from surface rust in the cylinders, but this doesn't mean there is actually a problem with the cylinders.  These numbers aren't super high.  And, in isolation, it is difficult to draw any conclusions.  It would be helpful if the owners was previously doing analysis so you can see the trend.

[MooneyAcolyte]

On 11/8/2020 at 11:32 PM, cferr59 said:

Sorry, I wasn't clear.  I was wondering how much calendar time is on the oil.  For example, if it was changed in 11/2019 and has 30 hours on it, it was sitting a lot and you would might expect to see high iron from surface rust in the cylinders, but this doesn't mean there is actually a problem with the cylinders.  These numbers aren't super high.  And, in isolation, it is difficult to draw any conclusions.  It would be helpful if the owners was previously doing analysis so you can see the trend.

Ah , I see. It was allegedly changed in June 2020. I've meanwhile asked the seller to provide a new sample after oil change and 10 hours of flying. Let's see what happens ....

[MooneyAcolyte]

On 11/8/2020 at 8:35 PM, carusoam said:

wanna,

I think you are missing a small detail here...

1) Hopefully, the owner has been doing oil analysis all along...

2) If he did it at 50hr intervals.... you can compare a new oil sample to the previous oil samples...

3) New oil has 0ppm of metals in it....

4) To get comparable numbers... you have to run the engine 50hours in a similar way...

 

5) The bad news... the chance of getting a Comparable sample is pretty slim without waiting a few months...

6) The good news... a plane with real metal problems... the numbers go so far off the scale, you aren’t seeing real metal problems with what you have...

7) If a plane is flying regularly... it has little chance of letting its cam and lifters croak...

8) If a plane is sitting idle... this type of oil analysis will give all kinds of erratic numbers...

9) Flying regularly, is good...

10) Not flying can be terrible, or not bad at all...

11) You will have better odds by looking at a cam follower or cam lobe...

12) But, by the time you have seen them all... you have just completed the effort of a top OH...

Buying a pre-flown plane can be a dice roll... or else they would cost the same as a new plane...

Minimize your risk wisely...   oil analysis done this way, is going to reject a lot of engines...

Hopefully this is helpful to put some context of what you are trying to do, with how good oil analysis really is...

PP thoughts only, not chem lab professor...

Best regards,

-a-

@carusoam Thanks much. 

Ad 1) Nope, he didn't. Makes me a bit suspicious.....

Ad 4) Of course. I was considering scaling it up assuming a linear build-up.

Ad 8-10) The seller says he is flying regularly, but there is no way for me to validate this other than an oil/filter analysis.

In summary: If the seller is motivated enough to provide the extra oil analysis, I'll take a leap of faith and go ahead with the purchase. If not - well ....

[LANCECASPER]

 

3 hours ago, wannabeMooniac said:

If the seller is motivated enough to provide the extra oil analysis, I'll take a leap of faith and go ahead with the purchase. If not - well ....

If the seller is crazy enough to put up will all of this nonsense he would be highly suspect. It's not hard to sell an airplane in today's market.  If it's still available after a period of weeks or months it has nothing to do with oil analysis.

A pre-buy at a legitimate shop would never put a seller through all of this. A proper contract signed before a pre-buy, with a non-refundable deposit, would let the Seller know that after the pre-buy that if he wants to continue, he would be responsible for any airworthy items - things that would ground the airplane at annual. If he doesn't want to do that then the deposit is refundable. Waiting for that first oil analysis to come back is not part of a pre-buy. If he's done regular oil analysis in the past and wants to show you, great, but not necessary. Making a person who wants to sell their airplane fly it another 10 hours to provide a completely meaningless oil sample, since there is no trend line, borders on insanity. You should consider analysis of a different kind, but it has nothing to do with your oil. 

[PT20J]

Chrome is high and iron is high which indicates cylinder/ring wear. Without a history it’s hard to tell what’s up, but normally one looks at this in combination with compression tests and borescope exams. 

I don’t think it’s that uncommon for these engines to need a top overhaul on the way to TBO.  And, I wouldn’t put too much stock in the time since overhaul because a lot depends on how long ago that was done and who did the overhaul and to what limits.

If all the other checks are good and you like the airplane and can agree on a price then buy it unless you are going to lose sleep worrying about the engine in which case you might want to pass. But remember you are buying a used airplane, and an old one at that. It’s always best to go into such a deal with a hefty cash reserve on hand because there will be surprises the first year or two. 

Good luck,

Skip

[Marcopolo]

7 hours ago, wannabeMooniac said:

Ad 8-10) The seller says he is flying regularly, but there is no way for me to validate this other than an oil/filter analysis.

Flightaware and FlightRadar24 should tell you any recent activity for this aircraft.

 

Ron

[Oldguy]

11 hours ago, wannabeMooniac said:

Ad 8-10) The seller says he is flying regularly, but there is no way for me to validate this other than an oil/filter analysis.

 

3 hours ago, Marcopolo said:

Flightaware and FlightRadar24 should tell you any recent activity for this aircraft.

If all else fails, look at the last annual inspection and compare the tach/Hobbs time on the log entry to what is currently on the plane.