M20K Oil Dipstick

[anthonydesmet]

Ok, here is a weird one I haven't experienced in 8 years of ownership for all you TSIO-360 MB, LB, GB owners:

 

Did a drive by the hanger last night just to check on her....plus check oil level from flight a week ago.  As background last weekends flight was first after an oil change in which 8 quarts was added.

Before last weekends flight when I checked the oil before my flight (which would have been after the oil change runup) my dipstick read a little over 5.5......I thought weird so I added a quart to 6.5.  Last weekend I flew for a little over an hour and then last nights initial reading roughly read 6.5 on the stick but it had some more oil on the sides of the stick going up to 8+ quarts so I wiped the stick off again and got a reading of 5.5 again, wiped off again and pulled a reading of a little over 6 quarts.....wiped stick off again and got another inconclusive reading up to about 8 quarts.....

I also noticed when I put the stick in one direction over the other the readings were different....I then played around with the dipstick and straitened it out best I could that would still allow it to go down the tube without getting stuck but that didn't make a difference. so my questions are:

1) is there a proper direction to put the dipstick in....loop facing forward or aft (pics below)

2) Is the dipstick supposed to have a required bend/curve?

3) is it possible the oil is getting wiped off by the side of the tube from the pull (would this happen more with clean oil than dirty oil)?

4) anybody else have this experience

 

I am not so concerned that I don't have oil in the case but more concerned that I want to track usage.

 

[carusoam]

Hot new oil is the most difficult to check with accuracy….

What happens….

The oil tube has enough oil stuck to the walls… that it is easy to get more oil on the stick while pulling the stick out…

If rotating the stick… the oil will get scraped off the tube onto the edge of the stick…

Making the oil fingerprint kind of resemble a U

So…

Try to ignore the oil that is on the edge of the stick….

And use the bottom of the U as the marker…

Hot oil has a tendency to make the U very thin and harder to see…

Clean oil has a tendency to be see-through making the U nearly invisible…

Where the stick sits in the bulk of the oil….  Will be the bottom of the U…

Try to pull the stick without rotating it…

An use a good light source…

The IO550 has a flexible cable for an oil stick…  with a flat blade at the end…  the flat blade sits in a small tube, while the rest of the cable is in a larger diameter…  Somebody designed it this way for unknown reasons…   But, it works well… 

PP thoughts only… not a measurement guru…

Best regards,

-a-

[Warren]

Not sure if this helps.  Looks like you have an MB engine.

On my K (LB engine, 231 model), the numbers on the dipstick face the front of the engine and the dipstick curves forward at the bottom.  I usually grab a light and rotate the dipstick 180 as I pull it out so I can see the numbers from the access panel without fully pulling out the dipstick.  Then, rotate 180 as I reinsert it.

The oil level also comes up if I leave it at least 24 hours after shutdown - increases .5 - 1.0 quart on dipstick.

Warren

[anthonydesmet]

14 minutes ago, Warren said:

Not sure if this helps.  Looks like you have an MB engine.

On my K (LB engine, 231 model), the numbers on the dipstick face the front of the engine and the dipstick curves forward at the bottom.  I usually grab a light and rotate the dipstick 180 as I pull it out so I can see the numbers from the access panel without fully pulling out the dipstick.  Then, rotate 180 as I reinsert it.

The oil level also comes up if I leave it at least 24 hours after shutdown - increases .5 - 1.0 quart on dipstick.

Warren

Thanks @Warren.  My mech told me today he just did a 231 (LB) oil change today and had same issue with consistent reading.  He wanted to see if it was just my airplane.  From the way you describe I think for me to match your technique with numbers facing forward (towards the prop) that would be my top picture posted above with the loop pointing towards the oil fill tube....which seems to give me the more consistent higher reading if use the bottom of the "U" as @carusoam described.

[Will.iam]

I thought i had a picture but i don’t.  I’ll check when i get home but I’m pretty sure mine is like your second picture. +1 on waiting 24hrs to get a better oil quantity reading. Mine goes up about a quart in 24hrs and slowly increases for days afterwards. I think i see about .25 of an additional quart by the end of the week and that was with 20w-50. With 100w AS it seems longer as i start with 6 quarts on the dipstick cold and upon shutdown will only show approximately 4.5. By the end of the week it’s back up to 6. 

[anthonydesmet]

32 minutes ago, Will.iam said:

I thought i had a picture but i don’t.  I’ll check when i get home but I’m pretty sure mine is like your second picture. +1 on waiting 24hrs to get a better oil quantity reading. Mine goes up about a quart in 24hrs and slowly increases for days afterwards. I think i see about .25 of an additional quart by the end of the week and that was with 20w-50. With 100w AS it seems longer as i start with 6 quarts on the dipstick cold and upon shutdown will only show approximately 4.5. By the end of the week it’s back up to 6. 

Yes - I usually wait a week.  This reading was about 7 days after the flight

[PeteMc]

I was told by a mechanic years ago for my 231 (GB and now LB) to only check the engine for oil level after it had been sitting for a day.  Too much oil get stuck up in the engine and it takes a while for it to drip down.

For multiple legs, just check to see that there is some oil on the dipstick and if there isn't oil all over the belly, then the levels are still good.

When I got my LB engine, that same mechanic took the new dipstick out and bent the tip a little, said it makes it easier to get the dipstick in....   But for the life of me sitting here right now, don't remember which way he bent it. 

And...   On my engine, I never fill more than 7 qts.  Any time I do, the extra immediately gets blown out, even with the oil separator.

[jlunseth]

It takes at least a day for the oil to drain out of the engine to the point where you can get an accurate reading on the dipstick.

My dipstick gives accurate readings if the ring is away from the oil cap/filler tube. My mechanic puts it in the other way about half the time, so there must be some Mooneys that need it that way, but the reading is way off and it is very hard to get the dipstick out.

[carusoam]

If you guys got the same tube as the IO550….   It is a larger diameter at the top, with a step halfway down to a smaller diameter…

The oil stick has no problem bumping into the step… 

 

imagine where the hole is and try to aim for it…

It gets extra goofy when the oil stick is half cable…

take a pic down the hole… you can see the issue…

PP thoughts only, not a mechanic..

Best regards,

-a-

[GeeBee]

I have an IO-550. I had inconsistent readings. Obviously you want to check after drain down, preferably a few hours or more. My mechanic however advised me all Continentals with wet sumps have a "capillary" problem. The oil will capillary up the tube and give a "high" bad reading with the stick installed. The only reliable way to check the oil is after drain down, remove the stick, wipe it, wait for the oil in the tube to drain back (about 30 seconds) insert the stick and then pull up and read the stick. 

Since I usually remove the stick in the hangar for insertion of the "engine saver" tube, on preflight of the cold engine I insert the stick, pull up and read. I have been getting very consistent and accurate readings. On the road, on a hot engine, I just make sure I have "some oil" and the belly and exhaust do not show signs of oil loss as there is no way you are going to get an accurate reading until drain down. That all said, I have found the hidden amount before drain down is about a quart. So on a hot engine, if it reads 5, I know I got 6.

 

[jlunseth]

Its about a quart, so if you just got out of the aircraft and want to read the oil, subtract a quart. Not perfect, but pretty close.

[A64Pilot]

1 hour ago, GeeBee said:

I have an IO-550. I had inconsistent readings. Obviously you want to check after drain down, preferably a few hours or more. My mechanic however advised me all Continentals with wet sumps have a "capillary" problem. The oil will capillary up the tube and give a "high" bad reading with the stick installed. The only reliable way to check the oil is after drain down, remove the stick, wipe it, wait for the oil in the tube to drain back (about 30 seconds) insert the stick and then pull up and read the stick. 

 

It took me awhile to figure out what the cause was on my baby Continental. a C-85. It’s  tube is huge, it doubles as the oil add tube. It would read at least a quart high when first checked, then correct on second check.

‘Same thing on my IO-520 years ago.

‘Anyway it’s two things, first the cap is air tight, second is the tube exits below the oil level in the tank, so when the engine cools. the air in the sealed tube pulls a slight vacuum, and sucks oil up the tube.

You really see this in marine engines because the tube is designed to be used to change oil so it often goes to the bottom of the pan even though most people insert a thin plastic tube inside of it anyway.

Ther trick as your say is to pull the stick and let the oil settle down and let the oil drain back off of the tube, because every time you pull the stick you drag some up the tube.

As I’m forgetful, first thing on preflight I’d pull the stick and wipe it off and stick it back in partially, leaving a whole lot sticking up, finish the pre-flight than go back and check oil. I did that because if I didn’t something would happen and I’d forget the stick was out and take off that way, but with it sticking out of the cowling that would be hard to not notice.

Edited June 17, 2021 by A64Pilot

[GeeBee]

1 hour ago, A64Pilot said:

You really see this in marine engines because the tube is designed to be used to change oil so it often goes to the bottom of the pan even though most people insert a thin plastic tube inside of it anyway.

That is a fact! I fight that engine too!

[Will.iam]

On 6/14/2021 at 9:48 PM, anthonydesmet said:

Yes - I usually wait a week.  This reading was about 7 days after the flight

Sorry was out on a trip longer than planned. I tried the other way and it was very hard to get the stick down and the oil was all over the sides making it difficult to get a good reading. This way in picture much easier to install and better readings for me. 

[milotron]

This is too funny. I don't have any images, but I just turned the dipstick around on the MB engine in my K as it was rubbing against the intake tube to the point the greenish paint had worn though. My ring now faces up, versus down. I didn't even considered whether it would read differently, but will look at it next time I am out, as I just changed it last flight.

My dipstick tube is also in a slightly different spot. I can't imagine any of this would affect the reading as the insertion length is all the same in the end.