Subscriber question:
"With an airplane piston engine, how much oil leakage is too much?" — Kris L.
Dean:
“It is difficult to achieve zero oil leakage on many aircraft piston engines. That makes it easy to become complacent, especially if your airplane has been leaking a small bit of oil for a long time. However, as in all areas of aviation, complacency is dangerous. Here are some indicators that might indicate a bigger problem:
If it’s dripping on the nose tire in a single-engine airplane. Engines sometimes leak a little oil out the breather tube after shutdown, but the tube outlet is usually away from the nose tire. If oil leaks on the nose tire, it is likely a significant leak that runs down the inside of the bottom cowling, making its way to the center aft area. This is an indicator that something is wrong.
If you can’t take a 4-hour trip with your airplane without worrying about the oil level. You have enough things to be thinking about in flight, without wasting mental energy on wondering if you will run out of oil in the engine.
If your oil consumption exceeds the manufacturer’s recommendation. Do some research for maximum oil consumption for your specific engine, and if it’s more than the recommended amount, it’s worth evaluating the situation.
Finally, if the line guy says, ‘That’s a lot of oil under your engine, we need to get that cleaned up,’ you have a problem. A big enough puddle on the ramp to attract attention probably needs a visit to the maintenance shop before your next flight.”
Do you fill your oil to the max level before flight?