[DanH]

Data point for the record. Photo below is a standard Lycoming o-360 (updraft sump for a carb), looking in past the #4 rod. The slots in the bottom of the case lead down into the sump; they are the oil drains. Here the sump is completely full to the top of the slots. With longerons level, the supplied dipstick indicates approximately 7.5 quarts.



BTW, with longerons level, 7.5 qts is below the rear prop governor drive gear. However, I'm pretty sure this gear is spinning semi-submerged when the tailwheel is down. Borescope through the rear case web into the accessory case:

 

[johnpaul44]

interesting, I take it not many run that high oil level, but interesting data point nonetheless. Im assuming its like a car with oil level, if the level gets high enough that anything that is spinning dips into it, it can cause foaming?

 

[texdog]

I’ve been keeping my oil level at 6 quarts for years. I now believe that 7.5 is better. I live in Texas and it’s hot. I think the engine O-360, is using the oil to help cool the engine. My normal oil temp is 190 plus. Aero Shell 100 year round.

 

[Larry DeCamp]

Data point for the record. Photo below is a standard Lycoming o-360 (updraft sump for a carb), looking in past the #4 rod. The slots in the bottom of the case lead down into the sump; they are the oil drains. Here the sump is completely full to the top of the slots. With longerons level, the supplied dipstick indicates approximately 7.5 quarts.

View attachment 69734

BTW, with longerons level, 7.5 qts is below the rear prop governor drive gear. However, I'm pretty sure this gear is spinning semi-submerged when the tailwheel is down. Borescope through the rear case web into the accessory case:

View attachment 69751

This is confusing me . I have always assumed that “proper oil level” corresponds to a known amount oil indicated on the stick after the oil galleries and filter have drained back to the sump and the tail is in the resting position on the ground. How else could you check the oil . This oil is available for use during operation, right ?

However, minimum oil quantity specifications by the manufacturer could mean “ less actual amount of oil won’t get sucked in the pump in level flight” or some other subjective criteria like ‘ a full tank of fuel won’t burn more than this much oil ‘

So, does “ minimum” take in to account all the issues Dan describes above or what ?

 

[Desert Rat]

This is confusing me . I have always assumed that “proper oil level” corresponds to a known amount oil indicated on the stick after the oil galleries and filter have drained back to the sump and the tail is in the resting position on the ground. How else could you check the oil . This oil is available for use during operation, right ?

However, minimum oil quantity specifications by the manufacturer could mean “ less actual amount of oil won’t get sucked in the pump in level flight” or some other subjective criteria like ‘ a full tank of fuel won’t burn more than this much oil ‘

So, does “ minimum” take in to account all the issues Dan describes above or what ?

Per Lycoming, the minimum safe quantity in the sump on most O360's is 2 quarts.

I'm not advocating running less than 5-6 quarts because it can cause oil pressure fluctuations and some other stuff, but it illustrates that if you keep it around 6 quarts you have gobs of margin before you get to whatever parameter Lycoming uses to define that minimum.

 

[uk_figs]

On my 0-360 it has always seemed that if I add 7 quarts it blows out a quart pretty quickly and then gradually reduces from 6 to 5 at which point it seems to stabilize and I get about 16 hours before I have to add another quart. Filling to 7.5 would likely get a lot of oil on the belly.
Figs

 

[Capt]

I run mine between 4-6 qts, done so with any 4 cyl Lyc’s

 

[DanH]

Couple notes...

I went with longerons level because that's where we spend most flying time. It's also the parking position for the A-models, and a common maintenance position for the tailwheel models. This is in fact an RV-8 with the tail on a stand.

I didn't mention minimum quantity and don't intend to do so. Personal preference is to run as much as practical. My interest is understand the why of breather oil transport.

In the first post we see how much the sump will hold before the level extends up into the crankcase. As noted, the stick indicates roughly 7.5 qts, which most folks consider too much. I plan to get similar photos after draining one, then two quarts. Notably I'd like to know how many quarts drops the level below the crankcase sump flange. Here's why. With oil at 7.5, the breather gas path is entirely through just three openings in the rear main bearing web, and that path would carry a lot of aerosol oil from around the whirling crankshaft. With the oil level below the sump flange, the breather gas has an additional path to the accessory case, through the drain slots and under the rear case wall as illustrated below. That path probably contains quite a lot less aerosol oil. Photo below is my 390.



I looked at the governor gear specifically because one of the available transport mechanisms can be described as slinging and splashing. Imagine that gear running partially submerged. It would throw oil 360 degrees, including upward in the accessory case toward the breather outlet, and transport oil to the idler gear above it by contact. For those who don't know, the outlet is at the end of the camshaft.

Note above, those of us with front mounted governors don't have any gears near the oil level.

Stay tuned.

 

[RV8JD]

Couple notes...

I went with longerons level because that's where we spend most flying time. It's also the parking position for the A-models, and a common maintenance position for the tailwheel models. This is in fact an RV-8 with the tail on a stand.

I didn't mention minimum quantity and don't intend to do so. Personal preference is to run as much as practical. My interest is understand the why of breather oil transport.

In the first post we see how much the sump will hold before the level extends up into the crankcase. As noted, the stick indicates roughly 7.5 qts, which most folks consider too much. I plan to get similar photos after draining one, then two quarts. Notably I'd like to know how many quarts drops the level below the crankcase sump flange. Here's why. With oil at 7.5, the breather gas path is entirely through just three openings in the rear main bearing web, and that path would carry a lot of aerosol oil from around the whirling crankshaft. With the oil level below the sump flange, the breather gas has an additional path to the accessory case, through the drain slots and under the rear case wall as illustrated below. That path probably contains quite a lot less aerosol oil. Photo below is my 390.

View attachment 69785

I looked at the governor gear specifically because one of the available transport mechanisms can be described as slinging and splashing. Imagine that gear running partially submerged. It would throw oil 360 degrees, including upward in the accessory case toward the breather outlet, and transport oil to the idler gear above it by contact. For those who don't know, the outlet is at the end of the camshaft.

Note above, those of us with front mounted governors don't have any gears near the oil level.

Stay tuned.

Dan,

Good stuff as usual. Just curious, why did you have to take the sump off in the first place?

(BTW, the tug has worked out very well. Thanks again!)

 

[RV8JD]

Dan,

Good stuff as usual. Just curious, why did you have to take the sump off in the first place?

Never mind, got the answer in another one of your posts this morning: "I'm doing an updraft conversion right now."

 

[DanH]

Actually I had the sump off the 390 to modify the intake flange, so I could bolt up an FM200 without a restriction. https://vansairforce.net/threads/intake-plenum-mod.226289/

Currently I am doing a fuel injection conversion on a parallel valve, updraft 360. It happened to need two cylinders, so it was a good opportunity to get the sump level data for that model.