O-320 blows 15w50 out of the breather but not W100

[FORANE]

My O-320A does just what the title says. Why is this?
Is it possibly related to the cam flinging thinner oil toward the breather; I have read this is possible. I have read some activities tend to increase oil out breather such as acro, flying higher, flying in turbulence, etc. I don't do acro, but do turbulence and over 10k on most flights. Additional background on my o-320, it has 10:1 pistons.

 

[Dan Thomas]

15W50 is an SAE 15 oil with viscosity modifiers. It's light stuff and will aerate easily. It's supposed to behave like a hot SAE 50 when it's hot.

W100 is an SAE 50 oil. Much thicker, but thins a lot when hot.

The O-320 isn't usually a problem this way. The small Continentals are the ones that typically don't care for multigrades, in my experience. They burn more of it, but don't lose it out the breather so bad. Is your breather off the top rear of the accessory case?

Dan

 

[FORANE]

15W50 is an SAE 15 oil with viscosity modifiers. It's light stuff and will aerate easily. It's supposed to behave like a hot SAE 50 when it's hot.

W100 is an SAE 50 oil. Much thicker, but thins a lot when hot.

The O-320 isn't usually a problem this way. The small Continentals are the ones that typically don't care for multigrades, in my experience. They burn more of it, but don't lose it out the breather so bad. Is your breather off the top rear of the accessory case?

Dan

Hey Dan

Yes, breather is in top rear of case and only about 2 inches under the cowl. Thus, the hose off the breather goes up about 1 inch then all downhill; I just cannot raise the air/oil separator to get any help from gravity.