Blow by and oil use

[Ragsf15e]

So I’ve read several Mike Busch articles on oil use, blow by and compressions.  I even reread the one about finding the source of oil use (leak, breather tube - Blow by past rings, or exhaust - in through valves and burned).  Other than that, I’m open for input on my engine, to include doing nothing...

The engine (io360A1A) has ~1000 hours smoh which was in 1998.  In 2004 it had a prop strike.  Inspection included new cam (unknown reason) and overhauled chrome cylinders.  I bought it in 2015.  It flys about 80 hours a year now.  It used 1qt/6 hrs for 4 years.  The oil always turned black within 2-3 hours of an oil change and the belly has some oil, but doesn’t seem like too much. 
 

In 2017 it got 2 rebuilt chrome cylinders due to wobbly exhaust valves.  Cam was inspected and looks good.  Last summer I noticed oil consumption increase to 1Qt/4hrs.  This January, the remaining 2 older cylinders both had some oil in them and the chrome was corroding off the inside.  I replaced the one that looked worse, maybe I should have done both?  Cam still looked fine (knock on wood).
 

The compressions are all above 75. The 3 new cylinders look good, I have never fouled plugs, but oil use is still pretty high (yes, chrome is normally a bit higher) at 1/3.5ish, maybe 1/4.  Oil turns black very quickly after change.  Oil analysis seems fine.  Engine runs good.

 

So, do I dig further?  Replace the remaining older/corroding cylinder next annual? 
 

Can it be blow by even with good compressions? Do I worry about it?

How do I isolate the problem without just guessing that it’s the oldest cylinder?  My IA borescopes and even checked the valves on the oldest cylinder.  Seems ok other than some chrome flaking off.

[Bob - S50]

30 minutes ago, Ragsf15e said:

So I’ve read several Mike Busch articles on oil use, blow by and compressions.  I even reread the one about finding the source of oil use (leak, breather tube - Blow by past rings, or exhaust - in through valves and burned).  Other than that, I’m open for input on my engine, to include doing nothing...

The engine (io360A1A) has ~1000 hours smoh which was in 1998.  In 2004 it had a prop strike.  Inspection included new cam (unknown reason) and overhauled chrome cylinders.  I bought it in 2015.  It flys about 80 hours a year now.  It used 1qt/6 hrs for 4 years.  The oil always turned black within 2-3 hours of an oil change and the belly has some oil, but doesn’t seem like too much. 
 

In 2017 it got 2 rebuilt chrome cylinders due to wobbly exhaust valves.  Cam was inspected and looks good.  Last summer I noticed oil consumption increase to 1Qt/4hrs.  This January, the remaining 2 older cylinders both had some oil in them and the chrome was corroding off the inside.  I replaced the one that looked worse, maybe I should have done both?  Cam still looked fine (knock on wood).
 

The compressions are all above 75. The 3 new cylinders look good, I have never fouled plugs, but oil use is still pretty high (yes, chrome is normally a bit higher) at 1/3.5ish, maybe 1/4.  Oil turns black very quickly after change.  Oil analysis seems fine.  Engine runs good.

 

So, do I dig further?  Replace the remaining older/corroding cylinder next annual? 
 

Can it be blow by even with good compressions? Do I worry about it?

How do I isolate the problem without just guessing that it’s the oldest cylinder?  My IA borescopes and even checked the valves on the oldest cylinder.  Seems ok other than some chrome flaking off.

Just a question for you.  What is your normal power setting at cruise (MP and RPM)?

[Ragsf15e]

Just now, Bob - S50 said:

Just a question for you.  What is your normal power setting at cruise (MP and RPM)?

2500rpm and I usually cruise around 8,500-10,500, so wide open throttle gives me about 19-22”.  I sometimes cruise LOP ~15 degrees, but if I’m going somewhere with the family I cruise ROP ~100.

[Bob - S50]

1 hour ago, Ragsf15e said:

2500rpm and I usually cruise around 8,500-10,500, so wide open throttle gives me about 19-22”.  I sometimes cruise LOP ~15 degrees, but if I’m going somewhere with the family I cruise ROP ~100.

The reason I ask is because I found that the closer I ran to square, the quicker I went through oil.  So for example, if you pull the RPM back to 2500 or 2600 in the climb, in my opinion that might cause more blow by.  If you cruised at lower altitudes at say 23" and 2400 RPM, again, just my opinion, that would cause more blow by than 21" and 2600 RPM.

My opinion is based on the theory that anything that creates a higher peak pressure will cause more blow by.  That could be lower RPM, higher MP, 50 ROP or a combination of those.

Again, just my opinion.

[carusoam]

Some things to keep in mind...

I’ll invite the new guy with a similar question... when I can remember.... where he is... 

 

We have two kinds of rings...

1) Compression... Great for getting good compression numbers...

2) Oil control.... Great for keeping oil in the sump...

Blow by has a tendency to pressurize the case...

3) Black oil... smells like exhaust, bubbly after flying, helps push oil out the case vent line...

 

4) Broken oil control rings, usually causes difficulty controlling where the oil goes...
 

5) Oil showing up in the lower plugs is bad...

6) oil showing up in the exhaust is bad...

7) Rings wear...

8) Cross hatch patterns wear...

9) visual inspection works wonders... get a dental camera going, post pics...
 

PP thoughts off the top of my head...

Best regards,

-a-

 

Invite for @Dialed In to join a similar discussion...

So you can see a similar challenge going on at the same time, find this thread...

 

 

[fboegner]

I had trouble with my IO360 w regards to oil consumption as well. I was at 3hrs per qt, also with oil visible in the spark plugs. When I had all 4 cylinders replaced last year, I noticed on broken oil control ring. I have also considered having the cylinders honed(?). In the end I opted for new ones. Now consumption is less than 1qt per 10hrs. I also cruise around 8-10k ft. 

[neilpilot]

Maybe I missed this above.....and this is so basic I'm reluctant to ask.  When do you top off your oil, and to what level?  If you fill your oil above 7qt, that first quart will leave pretty quickly.

[Ragsf15e]

2 hours ago, neilpilot said:

Maybe I missed this above.....and this is so basic I'm reluctant to ask.  When do you top off your oil, and to what level?  If you fill your oil above 7qt, that first quart will leave pretty quickly.

Yeah, I should have noted that but didn’t.  I just keep it at 6qts.  If I go on a 4 hour flight, I might start at 6.5, but generally just start at 6.

@Bob - S50 thanks for the comments.  I have been flying with higher MP / power more recently since I was breaking in the new cylinder I got in January.  Maybe I should just relax and see if it settles out when I go back to my normal higher altitude cruise.

@carusoam yes, I have suspected it could be an oil control ring issue on my remaining older cylinder.  Actually I was hoping to get lucky when I replaced a cylinder at annual in January, but that didn’t appear to change consumption.  We borescoped the cylinders and the last remaining original one is kind of corroded inside but not terrible. The others still look new.  Any way to be Semi-sure where the possible broken oil ring is?

[211º]

@Ragsf15e, this is related to oil consumption and case pressure.  After an annual, I noticed a quicker-to-black oil and greater consumption/use.  I'm not sure what type of oil pressure regulator you have, but if you have the ball-bearing-spring-containing, non-adjustable (well, adjustable with washers, not a wrench) type you might look to confirm that the regulator is installed correctly. I may be off base, but it seems that my use/issue went down quite a bit after I saw the this regulator was re-installed with the pass-through holes mis-aligned with the pass through holes in the case.

Edited June 9, 2020 by 211º

[Ragsf15e]

18 minutes ago, 211º said:

@Ragsf15e, this is related to oil consumption and case pressure.  After an annual, I noticed a quicker-to-black oil and greater consumption/use.  I'm not sure what type of oil pressure regulator you have, but if you have the ball-bearing-spring-containing, non-adjustable (well, adjustable with washers, not a wrench) type you might look to confirm that the regulator is installed correctly. I may be off base, but it seems that my use/issue went down quite a bit after I saw the this regulator was re-installed with the pass-through holes mis-aligned with the pass through holes in the case.

Thanks, I’ll look into that.

[bonal]

Another thing you might try is to use a compression tester and listen through the oil filling tube. If your getting blow by you will hear the air escape from the offending cylinder into the crank case.

private pilot only not an expert on anything 

Good luck

[Ragsf15e]

21 minutes ago, bonal said:

Another thing you might try is to use a compression tester and listen through the oil filling tube. If your getting blow by you will hear the air escape from the offending cylinder into the crank case.

private pilot only not an expert on anything 

Good luck

Good idea.  This is about where my understanding of oil control rings and compression testing ends... your theory sounds plausible, but all the compressions are real good.  Wouldn’t one of them be low if I was able to hear it leaking out?

 

[bonal]

Not always the case. I had a stuck oil ring and was using a bit more oil than normal found the culprit by listening through the oil tube that jug was in the high seventies on compression.  Also was evident by oil buildup on the lower plug but no evidence in the tail pipe in the form of burning oil. 

Personal experience only not an AP or IA 

Edited June 9, 2020 by bonal

[takair]

Had similar experience as Rags. Overhaul was roughly same time with CermNil cylinders. Oil burn was never great. Last fall it got really bad.  Good compression, good borescope, good oil analysis, oil in some plugs and dark oil soon after change. Finally started pulling jugs and all had bad compression rings. See picture. Turns out there were issues with cerminil rings and jugs back then. Over 40 hours on new nitride jugs and so far l am seeing over 10hrs per qt.   Knock on wood. 

[carusoam]

Wow!

Great pics!

OilP regulator and rings...

Parts we often don’t get to see...

 

When oil is getting away...

It often shows up somewhere...

If it is getting burned, it typically shows up during start-up smoke shows....

If it is a single offending cylinder, the lower spark plug may be the indicator... oily or crusted in burnt oil...

 

Pulling the offending cylinder to see what is going on seems to be a common next step...
 

PP thoughts only, not a mechanic...

Best regards,

-a-

[Tony G]

On 6/8/2020 at 9:10 PM, Bob - S50 said:

Just a question for you.  What is your normal power setting at cruise (MP and RPM)?

This actually a good question for the OP cos I was wondering what setting cruise of both  cos I have a guy who uses same setting..

[Ragsf15e]

I have one more piece of information and I’m really hoping this helps point to a possible source of my increased oil use...

I’ve always had some drips of oil out the drain from the mech fuel pump.  It’s been increasing so I had it replaced.  Oil stopped coming out of there, but both my mechanic and I noticed some oil (and a few drips of fuel which is normal) coming out the adjacent drain from the sniffle valve.  So how in the heck does oil get down the intake pipes and into the bottom of the intake manifold?  Maybe Leaky intake valve seals is all I could come up with after extensive Mooneyspace searches?  
 

The oil use is at about 3.5 hours/qt at this point, but it had been close to 6 hours/qt before I noticed it dropping.

 

 

[FloridaMan]

I remember hearing somewhere that it takes a long time for the rings to properly seat with chrome lined cylinders. I’ve been wrong at least once already today, but perhaps someone else can chime in. 

[takair]

7 minutes ago, Ragsf15e said:

I have one more piece of information and I’m really hoping this helps point to a possible source of my increased oil use...

I’ve always had some drips of oil out the drain from the mech fuel pump.  It’s been increasing so I had it replaced.  Oil stopped coming out of there, but both my mechanic and I noticed some oil (and a few drips of fuel which is normal) coming out the adjacent drain from the sniffle valve.  So how in the heck does oil get down the intake pipes and into the bottom of the intake manifold?  Maybe Leaky intake valve seals is all I could come up with after extensive Mooneyspace searches?  
 

The oil use is at about 3.5 hours/qt at this point, but it had been close to 6 hours/qt before I noticed it dropping.

 

 

I posted about my rings, but my #3 cylinder had oil getting into the intake manifold as well.  A few drips after each flight.  I suspected it was the intake valve, but the drip rate seemed too slow for my high burn rate.  Likely a contributor, but I don’t think it accounted for 2 or 3 hours per quart.  Since there are not really seals, likely the guides....

[Guest]

On 6/8/2020 at 11:36 PM, Ragsf15e said:

So I’ve read several Mike Busch articles on oil use, blow by and compressions.  I even reread the one about finding the source of oil use (leak, breather tube - Blow by past rings, or exhaust - in through valves and burned).  Other than that, I’m open for input on my engine, to include doing nothing...

The engine (io360A1A) has ~1000 hours smoh which was in 1998.  In 2004 it had a prop strike.  Inspection included new cam (unknown reason) and overhauled chrome cylinders.  I bought it in 2015.  It flys about 80 hours a year now.  It used 1qt/6 hrs for 4 years.  The oil always turned black within 2-3 hours of an oil change and the belly has some oil, but doesn’t seem like too much. 
 

In 2017 it got 2 rebuilt chrome cylinders due to wobbly exhaust valves.  Cam was inspected and looks good.  Last summer I noticed oil consumption increase to 1Qt/4hrs.  This January, the remaining 2 older cylinders both had some oil in them and the chrome was corroding off the inside.  I replaced the one that looked worse, maybe I should have done both?  Cam still looked fine (knock on wood).
 

The compressions are all above 75. The 3 new cylinders look good, I have never fouled plugs, but oil use is still pretty high (yes, chrome is normally a bit higher) at 1/3.5ish, maybe 1/4.  Oil turns black very quickly after change.  Oil analysis seems fine.  Engine runs good.

 

So, do I dig further?  Replace the remaining older/corroding cylinder next annual? 
 

Can it be blow by even with good compressions? Do I worry about it?

How do I isolate the problem without just guessing that it’s the oldest cylinder?  My IA borescopes and even checked the valves on the oldest cylinder.  Seems ok other than some chrome flaking off.

Oily cylinders tend to have good static compression values.  Continental engines published numbers for crankcase internal pressure limits with the engine running.  You connect a water manometer or an old airspeed indicator to an old oil cap and run the engine.  4” H20 or 90 MPH from my memory.  Sadly Lycoming does not publish numbers.

If your last cylinder is showing flaking chrome, it’s time for a replacement.  Chrome cylinders generally burn more oil and blacken it more quickly.

Clarence

[Rotorhead]

On 6/9/2020 at 12:10 PM, Ragsf15e said:

Thanks, I’ll look into that.

@Ragsf15e  Bringing this oldy back. Did you happen to look into what 211 mentioned and if so, did it make an appreciable difference?

[Ragsf15e]

1 hour ago, Rotorhead said:

@Ragsf15e  Bringing this oldy back. Did you happen to look into what 211 mentioned and if so, did it make an appreciable difference?

I didn’t mess with that since my oil consumption had changed with no appreciable mx done.  What I did do was replace the remaining chrome cylinder as it was flaking anyway.  That fixed the oil consumption back to normal (at least for chrome) of about 1qt/7.  The oil still blackens within ~10 hours, but theres less on the belly and less overall consumption.  BL- i think that cylinder had a lot of blowby.

[Yourpilotincommand]

Great read on this topic for me as I have the io360 A1A w chrome cylinders consuming about a qt/4hrs. I have a borescope and due to take a look at my valves.. I’m a Mike Bush fan hell yea! I’ve noticed in my previous borescopes my chrome cylinder walls look significantly different than the typical cross hatched pattern standard cylinders. So, how would I know if I have flaking? Does anyone have any pics with flaking? I’m ready to take a closer look at my cylinder walls. Cheers! And thanks! Once I do my borescope I’ll share pics here. Chris

[Ragsf15e]

7 minutes ago, Yourpilotincommand said:

Great read on this topic for me as I have the io360 A1A w chrome cylinders consuming about a qt/4hrs. I have a borescope and due to take a look at my valves.. I’m a Mike Bush fan hell yea! I’ve noticed in my previous borescopes my chrome cylinder walls look significantly different than the typical cross hatched pattern standard cylinders. So, how would I know if I have flaking? Does anyone have any pics with flaking? I’m ready to take a closer look at my cylinder walls. Cheers! And thanks! Once I do my borescope I’ll share pics here. Chris

I don’t have pictures, but it definitely looked less shiny and more dull/brown in places.

Good channel chrome does look different, it looks like a shattered window.  Spidery cracks down the sidewalls.

[Yourpilotincommand]

On 6/22/2022 at 6:07 PM, Ragsf15e said:

I don’t have pictures, but it definitely looked less shiny and more dull/brown in places.

Good channel chrome does look different, it looks like a shattered window.  Spidery cracks down the sidewalls.

Yes, my chrome does look like a shattered window pattern. At first I freaked out as I expected the typical cross hatch.