Oil level

[Hank]

2 hours ago, sdflysurf said:

Thank you for starting this thread.  So as a new aircraft/mooney owner I feel (feel as in nothing scientific here - gut telling me only) that my M20F likes to show about 5-6 on the dipstick and any more that I add has been ending up leaking/blowing/whatever out and appearing on the bottom of the plane.  Sounds like that is perfectly normal now and what exactly causes this?  My oil pressure and temp have always seemed fine, I was just getting concerned that I needed to keep a couple of qts of Aeroshell 100w+ in my baggage compartment.

I make sure to have at least 5-1/2 qts for local flying, and start trips at 6 to 6-1/2 qts. There's always one in the baggage area (or a partial quart); on ling trips I make sure to have a full one. Even in my short body, there's always room for a full quart and a partial quart.

[carusoam]

Sdf,

Some reasons for the oil venting overboard...

• The case has a pressure relief vent... at the top of the case.... connected to a hose that goes out the bottom of the cowling...
• More oil in the case... the closer it is to the vent...
• Higher angle of attitude on the climb... the closer the oil will be to the vent...
• The higher the MP... the more blow-by of exhaust may occur, pressuring the case...

If you fill the oil in the sump all the way to the top...

Perform a bunch of T/O and landings...

Climb out at high MP @Vx...

You may find about a quart of oil has come out the vent in a relatively short period of time...

 

don’t use this as an excuse to stop looking for leaks...

There are several, more common sources of oil leaks from seals to drain tubes that may have a drip coming out every now and then...

Many are easy to find and fix...

PP thoughts only,

Best regards...

-a-

[jonhop]

My oil strategy for the IO-360. 

Main mission, one hour to 45 minute flights per week with an occasional long cross-country of three hours or more.

Oil changes are completed by adding seven quarts + CAMGUARD. After engine run and inspection there is sevenish quarts of oil showing. With each subsequent flight the oil gets a little lower with evidence of oil escaping on to the belly, as well as the usual color change. When she gets put away, a small pool of oil can be traced from the drip pan to the rear of the gear door, to the breather hose before each flight.

When the dipstick lands between the four and six quart line, one quart of oil is added. At this point, there is much less evidence of oil escaping the engine but it is still flowing out of the breather hose onto the gear door/drip pan when parked. For flights greater than three hours, seven quarts go in. Upon landing, I've had between five to six quarts showing on the dipstick, while there is a good bit of oil showing up on the belly.

Oil temperature and pressures have been stable. 

Two additional quarts are carried in the baggage compartment. One quart is for when I hit the five quart line when away from home base and the other is because you never know when you will need it. During my PPL, I learned that carrying extra oil is easy and beneficial. 

[Releew]

I like to run at 6 quarts.  For flights longer than 2 hours I start with 7 quarts but believe it drops to 6 very quickly.  I would love to see a level sensor that could show actual (proportional) level in 0-100% increments so you could see in real time what engine settings and conditions effect level consumption. 

Rick

[N201MKTurbo]

1 hour ago, Releew said:

I like to run at 6 quarts.  For flights longer than 2 hours I start with 7 quarts but believe it drops to 6 very quickly.  I would love to see a level sensor that could show actual (proportional) level in 0-100% increments so you could see in real time what engine settings and conditions effect level consumption. 

Rick

It would be easy to make a capacitive level sensor that would replace your drop stick. You could mark the electrode just like a dipstick so you could still use it as a standard dipstick. You would need a simple connector for the wire so you could unscrew it. You could probably just add a terminal to the current dip stick and use it as the electrode.

It would be interesting to see what the level would do with the engine running, oil splashing around and such.

[jaylw314]

34 minutes ago, N201MKTurbo said:

It would be easy to make a capacitive level sensor that would replace your drop stick. You could mark the electrode just like a dipstick so you could still use it as a standard dipstick. You would need a simple connector for the wire so you could unscrew it. You could probably just add a terminal to the current dip stick and use it as the electrode.

It would be interesting to see what the level would do with the engine running, oil splashing around and such.

Probably not as interesting as this, but still mesmerizing...

 

[Shadrach]

Add a quart at 5, no more than 6 in the crank case.

Edited May 15, 2019 by Shadrach

[carusoam]

Great oil flow study, Jay!

The speaker is also describing flow around corners pretty well too... and effects of speed and temperature...

And interesting note regarding safety... 

Oil in a differential, is typically a higher viscosity, and lower temps than engine oil in an engine...

But the expectations are very similar... the oil will be spreading all over the place, leaving very little in the oil pan...

kind of explains how the first air bubbles start to show up in the oilP reading....

Best regards,

-a-

[sdflysurf]

On 5/13/2019 at 6:10 PM, carusoam said:

Sdf,

Some reasons for the oil venting overboard...

• The case has a pressure relief vent... at the top of the case.... connected to a hose that goes out the bottom of the cowling...
• More oil in the case... the closer it is to the vent...
• Higher angle of attitude on the climb... the closer the oil will be to the vent...
• The higher the MP... the more blow-by of exhaust may occur, pressuring the case...

If you fill the oil in the sump all the way to the top...

Perform a bunch of T/O and landings...

Climb out at high MP @Vx...

You may find about a quart of oil has come out the vent in a relatively short period of time...

 

don’t use this as an excuse to stop looking for leaks...

There are several, more common sources of oil leaks from seals to drain tubes that may have a drip coming out every now and then...

Many are easy to find and fix...

PP thoughts only,

Best regards...

-a-

Thanks guys - confirms all I've been wondering.  I have been told I could use an attitude adjustment so I'll check that first!

I concur with the others about starting with 7 at oil change, running between 5-6 for short flights, and 6-7 for longer flights with a qt or 2 in the baggage compartment for backup.  Oil pressure and temp have been in the green and anything over 6 usually comes out.  I'm having the engine compartment cleaned and I will watch for anything besides what comes out the vent.

[MikeOH]

11 hours ago, sdflysurf said:

Thanks guys - confirms all I've been wondering.  I have been told I could use an attitude adjustment so I'll check that first!

I concur with the others about starting with 7 at oil change, running between 5-6 for short flights, and 6-7 for longer flights with a qt or 2 in the baggage compartment for backup.  Oil pressure and temp have been in the green and anything over 6 usually comes out.  I'm having the engine compartment cleaned and I will watch for anything besides what comes out the vent.

Exactly my procedure, as well.

[hoot777]

I tend to agree that six quarts seems to be the sweet spot. I’ve had my G model for seven years and add seven when I change the oil. It smears on the belly and gets neat at six. I’m going to talk with my mechanic in July at annual but six quarts is a lot cleaner.

[Tx_Aggie]

Resurrecting this post for a further observation: my IO-360 also favors 6 quarts also. how long after a flight would it be reasonable to wait for the oil to drain to the sump and measure the oil level? I’ve noticed after long cross country flights the oil will show ‘lower’ when that last quart might actually just be spread around the engine taking time to reach the sump, maybe a viscosity thing?

[Ragsf15e]

4 hours ago, Tx_Aggie said:

Resurrecting this post for a further observation: my IO-360 also favors 6 quarts also. how long after a flight would it be reasonable to wait for the oil to drain to the sump and measure the oil level? I’ve noticed after long cross country flights the oil will show ‘lower’ when that last quart might actually just be spread around the engine taking time to reach the sump, maybe a viscosity thing?

I definitely notice this too.  Honestly, at least a couple days to get a good ballpark reading.  I notice the sump level higher still after a week!  By that point it’s going up pretty slowly though.  

It probably depends on how cold it is where the airplane is stored and what type of oil you’re using.  Cold temps and 100w oil probably drip down slowly.  Warm temps and multi weight probably quicker.  I have cold temps and multi weight, so who knows.

[A64Pilot]

Person I bought the airplane from wouldn’t add oil until close to 5, that made me nervous, so based on other aircraft I filled it to 7. In an hour and a half flight it blew it out until it got to 6, on the hour and a half flight back level still seemed to be 6.

‘So I guess the previous owner was right. 

If I want over 6 it seems I need to fit an oil sep, butI think I’ll just keep it at 6

[RLCarter]

TCDS for the IO-360 shows the following 
Sump capacity, qt.     8           
Usable oil qt,              6

so does this mean you can run it as low as 2 qts?

I keep mine at 7qts and wipe the belly

[PT20J]

15 minutes ago, Ragsf15e said:

I definitely notice this too.  Honestly, at least a couple days to get a good ballpark reading.  I notice the sump level higher still after a week!  By that point it’s going up pretty slowly though.  

It probably depends on how cold it is where the airplane is stored and what type of oil you’re using.  Cold temps and 100w oil probably drip down slowly.  Warm temps and multi weight probably quicker.  I have cold temps and multi weight, so who knows.

Kind of interesting. 

I tried a lot of oil levels with my factory rebuilt IO-360-A3B6. I noticed no difference in consumption running between 6 and 7 and 5 and 6. I did notice that oil pressure decreased some and oil temperature increased if it gets down to 4. But, it’s a new engine and the belly stays pretty clean. I wonder if age and perhaps the position of the breather tube makes a difference?

I also don’t notice any further increase in oil level after it sits for 24 hours.

Oil consumption decreased from 8-9 hrs/qt to 11-12 hrs/qt when I switched from A/S 100 to Philips 20-W50.

Skip

[Ragsf15e]

16 minutes ago, PT20J said:

Kind of interesting. 

I tried a lot of oil levels with my factory rebuilt IO-360-A3B6. I noticed no difference in consumption running between 6 and 7 and 5 and 6. I did notice that oil pressure decreased some and oil temperature increased if it gets down to 4. But, it’s a new engine and the belly stays pretty clean. I wonder if age and perhaps the position of the breather tube makes a difference?

I also don’t notice any further increase in oil level after it sits for 24 hours.

Oil consumption decreased from 8-9 hrs/qt to 11-12 hrs/qt when I switched from A/S 100 to Philips 20-W50.

Skip

I will add that I have chrome cylinders and an older engine so I get a little higher oil use and more on the belly.  I’m still surprised you don’t see it increase after 24 hours?  I’m in a real cold climate though, so once the engine cools, my oil is probably like ketchup until I preheat again...  I’ll have to track it closer this summer and see if it’s quicker.

I think it’s in the lycoming manual for the engine, that says the minimum is 4 qts.  Obviously the Mooney POH takes precedence, so I try to keep mine right at 6.

[PT20J]

Lycoming says 2 qts min. which seems really low. My M20J POH says 5qts min for flight in the limitations section. When I bought the plane the old engine was burning 2 hours/qt and on a long flight it got down to 4 qts. That's how I know that the temp rises at that level and it's probably why Mooney set the minimum at 5 -- it's probably based on the size of the oil cooler on a hot summer day.

Skip

[carusoam]

There may be value in knowing Lycoming has a 2qt minimum...

1) Not that you would want to T/O with only 2qts in the oil pan...

2) Its for when you have a major oil leak...

3) And you fortunately land at a field with services...

4) The 2qts you find left in the pan, pretty much indicates your engine didn’t run, starved for oil...   

5) anywhere close to having only 2qts in the oil pan... expect air to be drawn into the system generating an oil foam....

6) concentrations of bad stuff will be increased...

7) And all the other things that go with the limited volume of oil...

8) When it comes to oil.... more is better, until it pours out the case vent...

 

PP thoughts only...

Best regards,

-a-

[A64Pilot]

I believe the 2 quarts is called min bearing safe level, If I remember correctly from my IO-540, if for whatever reason you got below two quarts you were supposed to overhaul

‘So 2 quart is the min before damage can occur.

Our upper oil level limit doesn’t come from where you might think, we get from being car owners that we should run the oil at “full” on the dip  stick.

But where the upper level comes from on an airplane is take the max allowable oil consumption, which I think is just under a quart per hour on our 200 HP motors and then multiply that by the number of hours endurance of fuel you have, burning the max allowable amount of oil you can’t fall below the min safe level.

‘So most often the “full” mark on an airplanes dip stick is actually overfilled, so being overfilled it will expel the excess.

So if your like most and your oil consumption is something like 1 quart in 10 hours, then maybe you don’t need to be at the max fill limit.

‘Now some will do the math and say we don’t have over 6 hours of fuel on board, so that can’t be it. But Lycoming thankfully doesn’t have a different dip stick for every model of aircraft so if 8 is a little more than needed, that’s OK.

Edited March 21, 2021 by A64Pilot

[201Steve]

On 5/12/2019 at 11:13 PM, Joe Larussa said:

Ever notice a twitchy oil pressure reading below 6 quarts?

I made a cautionary landing under these conditions about a year ago. It was turning from daylight to dark, the factory cylinder head temp gauge has always been twitchy, and I had a lit runway directly beneath me. To this day, I don’t know if it was oil level, if my eyes were playing tricks, or if what my eyes saw was the known cylinder head twitchy gauge. Never seen it since on the oil pressure. Will never know. 

[EricJ]

3 hours ago, PT20J said:

Lycoming says 2 qts min. which seems really low. My M20J POH says 5qts min for flight in the limitations section. When I bought the plane the old engine was burning 2 hours/qt and on a long flight it got down to 4 qts. That's how I know that the temp rises at that level and it's probably why Mooney set the minimum at 5 -- it's probably based on the size of the oil cooler on a hot summer day.

Skip

Interesting.   For my early J model, POH 1220G only has temp and pressure for the oil in the limitations section, but section 1 says "6 qts min for flight".

[GeeBee]

Mike Busch

https://blog.aopa.org/aopa/2016/11/15/checking-the-dipstick/

 

 

[skykrawler]

I know of a club 172N model that had a Lycoming 320H2AD overhauled engine installed.  For whatever reason, it was a high oil user 4hrs or less to a quart and it would often get down to 4qts if allowed.   Engine ran to 2500 hrs and was removed for field overhaul and was running just fine.

On the other, after the overhaul and new cylinders  it stuck a valve, bent a pushrod and the tube.

 

[Ragsf15e]

4 hours ago, PT20J said:

Lycoming says 2 qts min. which seems really low. My M20J POH says 5qts min for flight in the limitations section. When I bought the plane the old engine was burning 2 hours/qt and on a long flight it got down to 4 qts. That's how I know that the temp rises at that level and it's probably why Mooney set the minimum at 5 -- it's probably based on the size of the oil cooler on a hot summer day.

Skip

Skip, They must have amended their guidance.  My poh is probably older than yours, but this is the only reference I can find in it:

Edited March 21, 2021 by Ragsf15e