The separator is nicely made of welded aluminum with stout inlets and outlets. To see if the M-20 Air/Oil Separator delivers on these claims, we installed one in our Mooney and flew it during a six-month, 120-hour trial. Second, the engine sump can be operated at a higher oil level, which theoretically improves lubrication and cooling. First, the aircraft belly stays cleaner, since the oil goes back into the engine, not overboard. The condensed oil is drained from the canister and piped back into the engine via the nearest convenient oil line.

The warm air then exits the canister and is dumped overboard, theoretically free of oil. In M-20 case, the guts of the device are a bit more complex, consisting of a series of internal tubes and a weir to catch and route liquid back to the crankcase.Once the breather output-which is a mixture of oil mist, warm air and water vapor-is inside the canister, its able to cool and condense. The output of the engines breather line is piped into one end of whats essentially a metal canister. Theres nothing mysterious or sophisticated about what an air/oil separator does. The latest of these gadgets comes from M-20 Oil Separators, the same company that developed a turbo-normalizing system for the Mooney M20 series.

These so-called air/oil separators purport to scavenge the oil vapor and dump it back in the crankcase instead of overboard, where it condenses on the belly.

Over the years, various devices to staunch the flow of oil mist have been tried. Some of that grunge finds its way onto the belly via engine oil leaks-major and minor-and the rest spews out of the crankcase breather line and the exhaust pipe. If theres another job as thankless as degreasing the belly of an airplane, it doesnt come immediately to mind.

Aig air oil separator review