Breather Oil at Altitude

In the last month or so I've had 30 hours of operation at >6000' airports, sig hours >8000'. At sea level I barely had any oil out of the breather tube. Now I find plenty. The rest of the engine is clean and I can clearly see from underneath the smear coming down on the exhaust pipe from the breather tube.

Is there any data about breather tube output at altitude? Anyone else seen this?

I suppose now I'll consider the air/oil separator.....

Blowby occurs from gasses sneaking past the rings and is due to the pressure differential between the combustion side and the atmo side (crankcase pressure). Dropping the Atmo pressure (alt increases result in lower atmo pressures) increases the differential, but doubt that it is significant enough to be noticeable, but maybe it is. The blow by increases crankcase pressure that is then equalized by expelling air through the breather. Air in the crankcase picks up atomized oil particles before being expelled.

Maybe an engineer will chime in on the significance of reduced crankcase pressures.

Larry

I should also add that previously if at altitude I was cruising. Now I'm coming out of fields with max rpm and climb rates at altitude....