I have a Comanche 250 and am looking at putting an oil separator on it this annual coming up. I have been doing some research and would appreciate some comments on the pro's and con's.

Thanks,
D. Schafer[/b]

Had a M-20 (model 300 I think) put in this winter. Very happy. Spend some time on the plumbing and your belly and pocket book will thank you.

Unless you have a wet vacuum pump, an oil sep is a waste of money, and perhapse even more important, damaging to your engine if you do not fly very regularly, and for at least 2 hrs at a time. Oil seps capture all of the stuff that comes out of the breather and condense it, returning the condensed goo back to the crank case. The breather was designed to vent all of this overboard. The water, the acids from combustion gasses blowby, and the oil mist all get captured. Some of the water vapor does vent out, but at a much lower rate than a free breather. Also in the winter time there is almost no chance that the steam will make it out of the seperator befor condensing and returning to the engine, where it will turn back to steam, and corrode and ruin your engine from the inside out. In the case of a wet pump, it is just the oil spray that gets collected and returned.

In the end I guess I must ask what it is you are trying to accomplish with the air oil sep. If it is a cleaner belly, get over it, buy some rags and only put 9 qts of oil in the sump, and wipe it down every 25 hrs or so. If the mess is bigger than that, and you are blowing lots of oil even at 9 qts or less, then you have other problems with excessive blow by, and you should address those issues first. Don't put a band aid on a gushing artery and expect it to fix anything.

-Zach