how much oil - M20J - IO-360-A3B6D

[dominikos]

I did a quick search on MS and I'm familiar with POH which states 6 qts minimum for flight... however, this is what previous owner shared with me with handover and recently tried it and it actually makes sense. If I keep oil between 6 and 5.5 qts, it actually does not fluctuate much. above 6qts and I have to keep adding. Here are his notes, any thoughts whether it is a valid approach? The only challenge is that keeping track of oil dropping from 6 to 5.5 on longer flights is PITA.

handover notes:

“if you fill with over 6 qts of oil, the engine will blow it out of the breather over time. One of my A&Ps told me to put only 5.5 - 6 qts of oil in it. This is commonly known issue with these engines. That’s why some people put an air/oil separator on them.

[ArtVandelay]

I have a air/oil separator and still blow out oil above 6.5, I usually keep it at 6, maybe a bit more if I have a long day ahead. I use about 1/2 qt every 10-15 hours.

[EricJ]

Yes, that's pretty common practice with any Lycoming xO-360 motor.   Anything over about 6 qts winds up getting frothed up by the crankshaft and susceptible to getting blown out the breather.   I try to keep mine between 5-6 Qts.

On an Arrow II, which also has a Lycoming IO-360, minimum safe operation is allowed down to 2 Qts.    

 

[PT20J]

I believe all the Lycoming 360 engines have a minimum oil quantity spec. of 2 qts. They also have a max oil consumption spec of about 2 hrs/qt. and a max capacity of 8 qts. This gives you enough oil capacity to never run out of oil before you run out of gas.

I have been associated with several flying clubs and FBOs with large fleets of Pipers and Cessnas equipped with Lycoming 320 and 360 engines. Standard practice has always been to run down to 6 and add a quart.

I have a factory rebuilt IO-360-A3B6 with a couple of hundred hours on it and have experimented with running down to 5, 5.5, and 6 qts before adding a quart. The oil consumption has been about the same as has been the minimal amount of oil on the belly.

I think as these engines age, blowby probably increases and they blow more out the breather. You can experiment and find a level that minimizes this. I have noticed that warm day oil temperature starts to rise (with a commensurate decrease in pressure) when the level gets down to 4 qts.

Skip

[carusoam]

So...

2qts is the minimum...

And OilT is the limitation...

So on really hot days, fill her up then clean her belly....

The case vent is near the back of the case... oil gets closer to the vent with nose up attitude...

You may see more oil go out the event if doing a lot of T/O and climbs...

PP thoughts only, not a CFI...

Best regards,

 -a-

[mooneyflyfast]

Also, don’t be in a hurry to add oil. The level will keep comming up for several days after you shut  it  down.  Wait a few days and if it is less than 6 qts. add 1 pt.

[EricJ]

1 hour ago, PT20J said:

I believe all the Lycoming 360 engines have a minimum oil quantity spec. of 2 qts.

The POH for my airplane says 6 qts is the minimum for flight.   The Lycoming xO-360 Operator's Manual says 2 Qts is the minimum safe level.

[carusoam]

More oil is better than less oil...

I high level of oil.... will be good for 

• Spreading contamination around resulting in lower concentration Of contaminants...
• Additional cooling from sitting in the aluminum oil pan for a longer period of time...
• Spreading degradation around resulting in lower concentration of degraded oil...
• Lower concentration of combustion by-products as well...

So...

If you fly around with a lower volume of oil in the oil pan... you may want to change the oil more frequently... based on concentrations of stuff you don’t want in there...

Interesting math...  If you start with six quarts of oil, and add a quart every 10 hours, then change the oil out at 50hours... how many quarts have you actually used?  Expect all the contaminants to stay in the engine until the oil gets changed...

PP thoughts only, not a mechanic...

Best regards,

-a-

[201Steve]

Another point to consider, if you spring an oil leak from any of the common leak points, you’re better protected from critical level. Not arguing for or against, just something I consider when deciding on quantity. 

[jaylw314]

32 minutes ago, 201Steve said:

Another point to consider, if you spring an oil leak from any of the common leak points, you’re better protected from critical level. Not arguing for or against, just something I consider when deciding on quantity. 

True, but that only helps for failure modes where

• You somehow know you're losing oil fast AND
• You wouldn't have made a precautionary/emergency landing anyway.

Unless both are true, having more oil at the start of flight doesn't buy you any time from an oil leak

[201Steve]

23 minutes ago, jaylw314 said:

True, but that only helps for failure modes where

• You somehow know you're losing oil fast AND
• You wouldn't have made a precautionary/emergency landing anyway.

Unless both are true, having more oil at the start of flight doesn't buy you any time from an oil leak

Not sure I’m following your logic. I’ve left the ground with a 100% leak free engine and landed 4 hours later with oil everywhere. Having more oil than less was better in this case. I didn’t know I was losing it and I did not make a precautionary landing. I just flew, landed, and then appreciated having a greater quantity of oil from the beginning. Ya dig?

[N201MKTurbo]

I can tell you from experience that if you have less than 2 qts. The prop goes crazy. It will get your attention. 
 

I believe the certification standard is the engine must hold twice as much oil as it takes to meet all the certification standards, with regard to oil temperature and such. So the engine should run all day at 100% power with 4 Qts. 

[A64Pilot]

The 2 quart level is a level that if you fall below will result in engine failure and if doesn’t I believe that oil level supposedly requires an overhaul.

The upper level is determined by hours of fuel on board of a standard airplane, then using the max allowable oil consumption multiplied by number of hours of fuel available won’t take you below the min safe level.

This is why identical engines in different aircraft will have different min oil levels according to the POH.

‘This is the formula used to determine max oil consumption for Lycoming’s 

.006 x BHP x 4 ÷ 7.4 = Qt./Hr.

https://www.victor-aviation.com/pdf/tech-docs/SI1427B.pdf

So if I do the math correctly, and check it cause I often mess up the math, but we are allowed to use .65 quarts per hour and it’s not excessive.

So take .65 quarts times the max time aloft we can achieve, add that to two and you will get the min oil level at take off.

Understand that’s MIN level, not recommended level and it allows for zero leakage. so a little extra can be similar to having a little extra fuel in the tanks

Most engines max level is above the point where it will blow out the excess, the engine manufacturers know that of course but that allowable level may be required in order to ensure some aircraft can use that engine due to the rather long endurance they may have.

‘For some reason STC’d long range or ferry tanks are not accounted for in this oil consumption formula, so it’s possible in theory to run out of oil if your ferrying an aircraft for example, why long range tanks don’t require higher oil levels I can’t explain, it would seem they should.

Who would fly a aircraft that burns a half quart an hour? 

 

Edited March 2, 2021 by A64Pilot

[N201MKTurbo]

Actually, what happens when you get below 2 Qts. is it forms a little vortex at the oil suction hole in your sump like the drain in a bath tub and starts to suck air into the oil pump. This will cause wild fluctuations in your oil pressure along with pushing air instead of oil to your bearings.