high oil consumption

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henryinparadise

Filing Flight Plan
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Henry
I have a 1973 C210 with a normally aspirated Cont.520 with 500 hrs on it.
Recent comp test shows 79 or 80 lbs on all cylinders.
It uses 1 qt every 2 to 2.5 hrs.
It sat for most of 2022 getting a new spar.
It does not leak or make a mess anywhere.
I run aero shell 5-35 but im switching to aeroshell 100.
The plane is in northern calif.
My mechanic is stumped but not concerned.
any ideas out there?
 
You're running what oil? The only piston multigrade shell makes is 15W50.

What level are you filling the crankcase to? If I keep mine at 12, it will lose it in short order. Mine will stay at 10.5 on the dipstick for a good long time.
Done an oil analysis?
 
Oil consumption can also be affected by stuck oil wiper rings--those skirt-side of the compression rings. The wipers can coke/gum up in their slot and get stuck. Are any of the spark plugs wet?
 
thanks Ron
i do run 15-50 and keep it around 10 qts.
I will do an oil analysis next week.
i bought the plane last nov.
the compression was low but with use it
came up nicely.
i was hoping that with use the oil rings
would clean up. i think that's the problem.
we may take off one cylinder to have a look.
any ideas are appreciated from anyone.
henryinparadise.
 
Domenick
that is exactly what i was thinking.
yes 4 of the bottom spark plugs get wet after
shut down.
does anyone advocate a gum out oil additive
like seafoam for a short period of time prior
to an oil change? too risky?
just an idea.
henryinparadise
 
Domenick said:
Oil consumption can also be affected by stuck oil wiper rings--those skirt-side of the compression rings. The wipers can coke/gum up in their slot and get stuck. Are any of the spark plugs wet?
Click to expand...
I agree and experienced the same thing. Removed the cylinders and cleaned the rings and pistons and put it back together. The oil consumption went way down.
 
Google "Mike Busch solvent flush".
 
Anyone has any experience of adding a litre of Mobile 1 5 hours before the oil change to clean the rings?
 
Oil can enter the cylinders from worn valve guides.
Are the plugs wet IMMEDIATELY after shutdown, or after sitting? I'd check at both times. Wear fabric garden gloves working on the hot engine.
After sitting overnight a borescope MIGHT show a wet valve.
 
Last edited:
Dana said:
Google "Mike Busch solvent flush".
Click to expand...
As usual, someone else’s work becomes Bush’s work. It was originally suggested by Ed Kollin…


With no more information than has been given, and oil consumption as bad as is being claimed, I don’t think I’d start there. First thing I’d want to know is where the oil is going and how it is getting there. With that much oil being consumed i would think it would be pretty easy to figure out.
 
Has your mechanic used a borescope to examine inside each cylinder? If one cylinder is a lot wetter than the others, replace it and your problem may go away. That’s what I did with a similar engine, IO-550.

Stuck rings can be the cause of oil consumption, and wet cylinders are a possible symptom to identify the culprit cylinder. Requires borescope, and for that you want a mechanic who uses one regularly, not one who usually just does compression checks.
 
Thanks for everyones' responses.
The lower plugs are wet, hot & cold.
We borescoped the engine recently.
Im going to research Bush's solvent flush now..
Its getting an annual right now.
Im going to see if he will pull the worst
cylinder and see whats up.
Thanks again.
 
Domenick said:
Oil can enter the cylinders from worn valve guides.
Are the plugs wet IMMEDIATELY after shutdown, or after sitting? I'd check at both times. Wear fabric garden gloves working on the hot engine.
After sitting overnight a borescope MIGHT show a wet valve.
Click to expand...
Yep, if the lower plugs are wet after sitting, worn valve guides is a good guess. And it would explain the high compressions (piston rings and valve seals are fine, that's not where you're losing oil). Lycoming has a wobble test your mechanic can do, maybe Continental does too.
 
From the C206 maintenance manual inspection checklists. The 206 has the same engine:

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A coked/sludged-up crankcase breather line raises case pressures, hampering oil ring performance.

Take the oil filler cap off and blow into the crankcase. Air should pass through and out of the breather easily. Don't use compressed air or you could blow the front seal out if the line was blocked enough.
 
henryinparadise said:
Thanks for everyones' responses.
The lower plugs are wet, hot & cold.
We borescoped the engine recently.
Im going to research Bush's solvent flush now..
Its getting an annual right now.
Im going to see if he will pull the worst
cylinder and see whats up.
Thanks again.
Click to expand...
Late to the party, but that's pretty high consumption for a 500 hour engine. Could be an issue with the oil control ring, could be glazed rings. Could be valve guides/clogged breather, especially if it doesn't ever drip a drop.

Generally a properly broken in -520 or -470 will burn a quart in 12 to a quart in 20 during the first 20 hours after an oil change if filled to it's happy point which is typically 9-10 quarts.

Where in Norcal? There's a good 210 guy there. PM if interested. If the carry through spar was replaced for corrosion after failing the AD, then a lot of money has been invested in the bird. Maybe a top overhaul with new cylinders in its future assuming the cam and lifters look good (did they?). Maybe it's just unclogging something that is presently clogged.
 
Wet plugs is the clue. The most likely culprit are worn/broken/stuck oil control rings in one or more cylinders. Removal or borescoping the oily cylinder(s) will reveal if there is other contributing cylinder wear. How to solve the issue depends on what you find. Worn/broken rings won't fix themselves and may cause more damage if not addressed. Compressions won't necessarily tell you much. An oiled up cylinder with bad oil control rings can still give decent compressions while pumping oil during operation.
 
Lots of good ideas.
Thanks to all.
I read Mike Bush's and the other solvent flush instructions.
I always start with the cheapest n easiest solutions on
mechanical problems.
So ill do a solvent flush after the annual is done.
Cost- about $200?
If that doesnt work we can take one cylinder off.

The plane did have the spar replaced before I bought it.
It sat for most of 1 year.
Im really thinking / hoping its the oil rings.

Thanks Again
 
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