Brad

I have been going trough a lot of trouble shooting on my Legacy IO-550exp related to oil blowby. I have the Andair separator. My problems related to two issues.  If you are blowing a lot of oil this system can be overwhelmed and if it fills to the outlet port. You will really start blowing oil because of back pressure.  I originally plumbed into the accessory case for the drain back oil with poor results on long trips.  Lancair recommended this but Continental, Airwolf, M20, Cirrus all say the only low pressure place to return oil is the rocker valve cover or push rod tube.  The accessory case sees high crankcase pressures and has oil spraying onto the port. I also tried a remote collection cup sold by Andair which worked OK till it filled. I am now plumbed into the rocker valve cover with good results but do not have enough data on long flights to be sure. Many of these systems rely on pressure from a vacuum pump to aid siphoning back to the crankcase.  Without that you have a little disadvantage and be sure there is good gravity feed back to the engine.   

Why am I loosing so much oil?  I think oil levels play a very important part in this and would like to hear from others on their opinion.  I originally ran at 6 quarts because the common wisdom was that anymore and it would just get blown out the breather. I am worried that anything less than 6 could cause cavitation and foaming in the oil pan and accelerate the oil blowby problem. Cirrus specifically recommends not letting the level drop below 6. Not a lot of fun watching oil pressures drop from 75 to 50 and getting out of the plane and having the belly smeared with oil. I am now running closer to 7 and hope this gives better results.

My oil temps run near 180 and have never gone above 200 except during extended ground operation. I have the oil cooler door and tried removing it because I never used it but my oil temps were to low in the winter.  Home base Vermont.

Hope to visit with a lot of you at Oshkosh.