Oil dipstick markings.

[Will.iam]

Every oil change i have done once the engine is started and ground run to verify for oil leaks the oil dipstick shows 1 quart lower than what i put into the engine. My first couple of oil changes i thought i had miss counted the number of quarts i put in but nope multiple oil changes later i am confident i put 6qts in and that includes filling up the oil filter as mine is mounted vertically and i can fill the filter full before installing it.  And with only running the engine for a few mins at idle power there is no way the engine is blowing the oil out or burning a quart in that short of time. It makes me wonder if the oil dipstick was calibrated for oil levels when it didn’t have an oil filter installed and just a screen or maybe i have the wrong dipstick for my engine. My question is my engine likes to blow out oil at 6qts but settles down at 5qts but that is really 6 known qts in the engine total. So when the dipstick shows 4.5 qts my poh says i need a minimum of 5qts for flight but i know there are 5.5 qts in the engine including the oil filter so is that limitation on the dipstick or what’s known in the engine? Are other tsio-360mb engine owners seeing the same thing or do i have an incorrect dipstick for my engine? Just curious. 

[M20F]

Hoses, oil coolers, etc. have oil in them as well, when you drain the oil they are empty and need to refill.  
 
If you put in 6, run it, and it reads 5.  Put 7 in, should read 6 once you run it.  

[EricJ]

The sum of all of the oil galleys, hoses, tubes, heads and surfaces that it'll adhere to adds up to quite a bit.  A fair amount goes into the prop and governor as well.
   

[PT20J]

The dipstick should have a part number on it somewhere. You could check it against the IPC for your engine to confirm that it is correct.

[Rick Junkin]

36 minutes ago, Will.iam said:

My question is my engine likes to blow out oil at 6qts but settles down at 5qts but that is really 6 known qts in the engine total.

I’m no expert but I am a scientist and engineer. Logic tells me that 5 qts is the sweet spot for your engine, from what you’ve described. Incidentally I’m surprised that 5 qts is the POH minimum for flight with a 6 qt sump. For comparison my 540 has a 10qt sump with a 6 qt minimum for flight. 4 qts is the minimum for… something I can’t recall off hand.

A couple questions. When you bring the sump back up to 6 qts after you’ve done the post-oil change run-up, how long does it take to blow that qt out back down to 5 qts? Once you’re at 5 qts, what is your oil consumption rate? 
 

I ask because I’ve been running my 540 at 8qts and always have some oil on the belly. @donkaye posted about having the same issue and being advised to run at 7 qts (?) where he didn’t get oil on the belly. I’m coming up on an oil change and I’m going to see how 7 qts works for me.

 

[Pinecone]

TSIO-360 will read low unless you let it sit overnight.  It takes a while for the oil to drain down.

Mine -SB is happy at 8 quarts.  Strange that different engines are so different.

IIRC FAA requirements are that the minimum allowed is no more than 1/2 the total capacity.  So some engines have an artificially high total oil, that will not stay in the engine.

[Will.iam]

1 hour ago, Rick Junkin said:

I’m no expert but I am a scientist and engineer. Logic tells me that 5 qts is the sweet spot for your engine, from what you’ve described. Incidentally I’m surprised that 5 qts is the POH minimum for flight with a 6 qt sump. For comparison my 540 has a 10qt sump with a 6 qt minimum for flight. 4 qts is the minimum for… something I can’t recall off hand.

A couple questions. When you bring the sump back up to 6 qts after you’ve done the post-oil change run-up, how long does it take to blow that qt out back down to 5 qts? Once you’re at 5 qts, what is your oil consumption rate? 
 

I ask because I’ve been running my 540 at 8qts and always have some oil on the belly. @donkaye posted about having the same issue and being advised to run at 7 qts (?) where he didn’t get oil on the belly. I’m coming up on an oil change and I’m going to see how 7 qts works for me.

 

My engine will take 8qts i did that once! As 2 qts left after a 20 min flight and i had a golden belly to wash off. After that no more than 6 go in and that stopped the fresh golden oil soaking the belly got. Now i have the black oil that shows its staying the engine long enough to turn dark as it slowly goes overboard to 5qts. At that level it slows considerably and much less belly cleaning. With my engine at TBO i know that is largely blow-by that is keeping me from holding more. It’s just if i put in 8qts i would be reading 7qts after an idle runup so like a pistol after cambering a round if i still want 8 in the magazine i would have to add another qt of oil and yes this is all checking 24hrs after 20w-50 or 48hrs 100W to let the oil drain back down as checking right after shutdown will show 2 qts low. That’s why i suspect my dipstick is off by a qt as you want to know what’s in the engine total. To put it another way, i have heard other pilots comment their engine spilts out 2 QTs and likes 6qt of oil. Well is that 6qts on their dipstick which in my case would be 7qts? Or does their dipstick read 7qts when they put in 6qts and then when they run their engine the level then shows 6qts on their dipstick after a day or two sitting to let the oil drain down?

[Marc_B]

https://www.aopa.org/news-and-media/all-news/2016/november/15/checking-the-dipstick
 

Engines are certified to be operational with half the oil capacity.  There is a sweet spot where your  engine isn’t spitting out oil on the belly and your oil “consumption” actually reflects the oil consumed rather than oil ejected on the belly.

The time that I actually keep higher than that is on long cross country trip where I utilize the heat capacity of an extra quart of oil for cooling.

Regarding drop in oil readings after shut down from preflight…there is so much oil slung around the inside of the engine, throughout the hoses, oil cooler…more accurate reading is taken at preflight.

I find my oil consumption most stable between 5.5-6.5 qts.  So I typically aim for 6.  Long cross country I’ll up to 7 qts.  (Conti TSIO360SB2, sump 8 qts)

[kortopates]

My engine will take 8qts i did that once! As 2 qts left after a 20 min flight and i had a golden belly to wash off. After that no more than 6 go in and that stopped the fresh golden oil soaking the belly got. Now i have the black oil that shows its staying the engine long enough to turn dark as it slowly goes overboard to 5qts. At that level it slows considerably and much less belly cleaning. With my engine at TBO i know that is largely blow-by that is keeping me from holding more. It’s just if i put in 8qts i would be reading 7qts after an idle runup so like a pistol after cambering a round if i still want 8 in the magazine i would have to add another qt of oil and yes this is all checking 24hrs after 20w-50 or 48hrs 100W to let the oil drain back down as checking right after shutdown will show 2 qts low. That’s why i suspect my dipstick is off by a qt as you want to know what’s in the engine total. To put it another way, i have heard other pilots comment their engine spilts out 2 QTs and likes 6qt of oil. Well is that 6qts on their dipstick which in my case would be 7qts? Or does their dipstick read 7qts when they put in 6qts and then when they run their engine the level then shows 6qts on their dipstick after a day or two sitting to let the oil drain down?

Will you are over complicating it or over thinking it.
The dip stick is very simple, it measures how much oil is in the sump! Not the engine.
it’s entirely normal after doing an oil change and filter that after you add 8 qts - into the sump where you dip stick should also confirm 8 qts and then after you run to leak check the oil level
in the sump will drop to 7 qts.
7 qts because the oil filter was empty till you ran it, which is between 1/2 to 3/4 qt and after running it you have at least 1/4 qt in addition to oil filter in other places.
The oil stick was never intended to tell you how many qts are anywhere else but the sump.
The only time you can validate the stick is accurate is after draining all the oil in the sump during your oil change and then add x qts of oil and your stick should show x qts.


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[OR75]

in this new world of GA I had to wait 5 weeks for a part. I took that as an opportunity to change the oil. And since I had plenty of time I let it drain for almost 4 weeks and flushed the oil cooler.

Usually, when I change the oil, I let the oil drain a day or 2

I was amazed how much oil dripped in 4 weeks - my guess is like 1/3 quart

the bonus is after I ran the engine, the oil was still a light yellow color.  Usually it darkens pretty fast with what was left in the sump.

if you have a plane sitting in a shop a few weeks and have the oil changed, asked them to drain the oil at the start and let it drain as long as it sits there. 

 

 

[Will.iam]

18 minutes ago, kortopates said:

Will you are over complicating it or over thinking it.
The dip stick is very simple, it measures how much oil is in the sump! Not the engine.
it’s entirely normal after doing an oil change and filter that after you add 8 qts - into the sump where you dip stick should also confirm 8 qts and then after you run to leak check the oil level
in the sump will drop to 7 qts.
7 qts because the oil filter was empty till you ran it, which is between 1/2 to 3/4 qt and after running it you have at least 1/4 qt in addition to oil filter in other places.
The oil stick was never intended to tell you how many qts are anywhere else but the sump.
The only time you can validate the stick is accurate is after draining all the oil in the sump during your oil change and then add x qts of oil and your stick should show x qts.


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Great so then is the poh minimum 5 qts for flight based on the dipstick or what is known in the engine? That’s the question. Because my breather slows way down at 5qts on the dipstick (6 in the engine) and practically non-existent at 4qts on dipstick (5 in the engine) buuuttt the minimum is 5. I guess i would be on shaky ground if i got ramp checked and didn’t add another qt on the spot if he was standing there watching. 

[Will.iam]

6 minutes ago, OR75 said:

in this new world of GA I had to wait 5 weeks for a part. I took that as an opportunity to change the oil. And since I had plenty of time I let it drain for almost 4 weeks and flushed the oil cooler.

Usually, when I change the oil, I let the oil drain a day or 2

I was amazed how much oil dripped in 4 weeks - my guess is like 1/3 quart

the bonus is after I ran the engine, the oil was still a light yellow color.  Usually it darkens pretty fast with what was left in the sump.

if you have a plane sitting in a shop a few weeks and have the oil changed, asked them to drain the oil at the start and let it drain as long as it sits there. 

 

 

I often wonder adding a qt of marvel mystery oil right before you warm up the engine to change the oil doesn’t help as it “thins” the oil and it drains much quicker than a normal change. 

[M20F]

1 minute ago, Will.iam said:

i would be on shaky ground if i got ramp checked and didn’t add another qt on the spot if he was standing there watching. 

I wouldn’t be worried about a ramp check, I would be worried about wrecking my engine by having insufficient oil in it. 
 
 

[kortopates]

34 minutes ago, Will.iam said:

Great so then is the poh minimum 5 qts for flight based on the dipstick or what is known in the engine? That’s the question. Because my breather slows way down at 5qts on the dipstick (6 in the engine) and practically non-existent at 4qts on dipstick (5 in the engine) buuuttt the minimum is 5. I guess i would be on shaky ground if i got ramp checked and didn’t add another qt on the spot if he was standing there watching. 

Dipstick as its the only measurement we have. We can only guess what's "in the engine" and we'll still be wrong because it will depend on how long we wait for it drain down where its its measurable.

Forget about what's "in the engine" (its unknown and not measurable) and just go by what the dipstick shows when the engine is cold before first flight of the day. All while realizing there is more oil in other parts of the engine that are not measurable and don't count towards the minimum oil.  You don't have to worry about your engine oil just after shutdown. The best time to measure it is when its cold just before flight. With the caveat that if your oil consumption is abnormally high and you are doing a long day of flying, say a couple 3 hrs flight and therefore need to make sure you have more than the minimum oil for the next leg and then measure the oil hot and assume its reading about 1 qt low from what it would be before adding another quart.

Here are some more details on this from Mike B

https://www.aopa.org/news-and-media/all-news/2016/november/15/checking-the-dipstick  

 

Additionally I'll comment that IMO too many people get carried away with optimizing oil consumption to a minimum. But remember oil has 2 purposes i) lubrication and ii) cooling. Don't get so carried away in reducing oil consumption that your running perpetually with low oil such that areas are running hotter than they should be with more oil in the sump, such as valve guides.

Edited October 26, 2024 by kortopates

[bigmo]

I never think of the dipstick as a way to check what’s in the motor - it’s just a gauge I can’t read from the cockpit. For my plane, anything over 7 I wind up wearing the first flight. At 7 I’m good.

I wait until I hit 6, then add a full quart. If I go below 6 (and I won’t), long climbs (SL to 8-9k) bring my oil temp up to a number I don’t like. 

Im not 100% sure I understand this whole thread. It’s not something I’ve ever really thought of. 
 

[Z W]

Mine is the same - put 8 quarts in at oil change, it will read 7 on the dipstick after first run.  If I add another quart then to go back up to 8 quarts on the dipstick (which is in reality 9+ quarts in the engine), it blows out pretty quick.  It holds between 6 and 7 on the dipstick pretty good so I let it get a little below 6, then add a quart.  I believe this maintains 7-8 quarts actually in the engine.

It used to hold less and would blow out anything over 6, so I would only put in 7 quarts at oil change, which would then read 6 quarts on the dipstick, and wait until 5 quarts to add, which did work fine.  Cleaning the oil and sludge out of the air/oil separator and replacing the oil cap gasket seemed to help and now it'll hold another quart.  I believe that reduced the crankcase pressure, or helped it properly escape the engine.

[Fly Boomer]

15 hours ago, Will.iam said:

if i got ramp checked and didn’t add another qt

FAA doesn't care about your engine unless it blows up and causes a forced landing.

[N201MKTurbo]

If you really want to drain all the oil, remove the suction screen. It is at the back of the sump. The drain is in the middle of the sump. The engine usually sits a bit nose high, so there is oil trapped at the back of the sump that won’t drain out.

That is for a Lycoming. Not sure about the Continentals.

[cliffy]

If you read the Lycoming manual for the 4 cyl engines it says min safe  oil level is  2 qts and the consumption can be 0.8 quarts per hour for 

the O-360 and 0.89 quarts per hour for the IO engines. 

This was even published by Mooney in one version of their Service and Maintenance Manual

Way lower and way more than most think and still be considered OK by Lycoming.  

Don't have the 6 cyl numbers handy

[bigmo]

1 hour ago, cliffy said:

If you read the Lycoming manual for the 4 cyl engines it says min safe  oil level is  2 qts and the consumption can be 0.8 quarts per hour for 

the O-360 and 0.89 quarts per hour for the IO engines. 

This was even published by Mooney in one version of their Service and Maintenance Manual

Way lower and way more than most think and still be considered OK by Lycoming.  

Don't have the 6 cyl numbers handy

That sounds crazy…but 100% right. I have two strikes that burn considerably less oil lol.

My burn rate is definitely not linear until I’m below 6 on the dipstick. At that point, I think I’m less than a quart per 8-10 hours. It’s slow for sure. Above 6 on the stick is probably one quart per 5-6. Above 7 is a quart an hour and then 3 hours cleaning the belly on my creeper. Lesson learned.

[Greg Ellis]

For those with Lycoming engines that are interested in what Lycoming considers maximum oil consumption, here is a formula they put in their break in service instruction back in 2010.

“The following formula is used to calculate the maximum allowable oil consumption limits for all Lycoming aircraft engines.”

0.006 x BHP x 4 ÷ 7.4 = Qt./Hr.