Tips for Turbine Engine Oil Servicing

January 2020

If you are continually topping off your aircraft’s engine oil to get the quantity/level indication back up to the full mark, you are likely to be over-servicing your engines. This occurs when too much oil is added to an engine.

To the uninitiated it may not seem like a big deal, but there are several things that could potentially happen as a result of over-servicing engines, including:

1. High-Pressure Stress: This occurs because too much oil can cause the oil pressure to increase and become excessive. Excessive pressure puts extreme stress on the gearbox seals and can lead to the second consequence.
2. Gearbox Seal Failure: Failure of the gearbox seal could induce oil leaks and cause visible streaking on the engine cowling. Gearbox seal failures require the aircraft to be grounded for servicing.
3. Dirty Cowling: When an engine has been over-serviced, the surplus oil ends up blowing out the breather, causing excessive oil streaks on the cowling.
4. Unnecessary Expense & Downtime: Often the first thought when spotting excessive oil streaking is to think you have an engine leak. This leads to the additional time and expense of grounding the aircraft to investigate, only to discover the engine is venting excess oil as a result of over-servicing.

Five Ways to Avoid Over-Servicing Engines

There are steps any flight operation can take to guard against over-servicing engines. Our top advice is as follows:

1. Service the oil within a specified amount of time after shutdown (different engine models have different times listed in their respective maintenance manuals, typically ranging from 15 to 45 minutes). Allowing the oil to stabilize after shutdown is the key.
2. It is our highest recommendation that you always fill the engine oil to levels specified in the aircraft’s maintenance manual.
3. Engine OEMs publish information and ‘how-to’ videos on proper oil service for specific models.
4. Understand your engine’s personality. One engine may show no significant consumption if maintained at half a quart low while at the same time, the other engine is maintained at three-quarters of a quart low. Servicing the oil to the proper level of each engine in many cases will show a decrease in oil consumption.
5. After filling oil to proper levels, always check the O-ring on the servicing cap is in good working order. Replace if necessary. If the O-ring fails inflight, all the oil could escape from certain turbine engine models, causing an unsightly streak down the side of the aircraft. This sudden oil loss could also cause significant internal engine damage.

Maintain Your Engine Oil Consumption Logs

Monitoring your engine oil consumption is an essential step in maintaining a healthy engine. A simple log that both flight crew and maintenance personnel have access to would suffice, as well as a proper understanding of when to service the oil.

Be aware that when the aircraft is away from home, the adding of oil isn't always communicated back to maintenance. Nevertheless, flight crews will need to answer what the oil consumption is if they have an issue.

Troubleshooting oil consumption isn’t always easy because some leaks are internal and would never be seen. A simple oil consumption log on hand would be a great benefit.