Plane & Pilot
Tuesday, October 22, 2013

Issues With Oil

Oil may be more important than fuel

Too little can be a major problem. For the pilot, fluctuating oil pressure could be a sign that the engine is running low on oil. This may mean air bubbles are being fed to critical bearings rather than lubricating oil, causing unnecessary wear.
The more frequently an airplane runs, the longer it's liable to continue running.
Conversely, you may have little or no warning that you're low on oil until it's too late. I once delivered a new Cessna T-Stationair to Sydney, Australia, and on the initial 14-hour overwater leg from Santa Barbara to Honolulu, the engine burned 10 quarts of oil. All temperatures and pressures remained normal, and the big Lycoming ran great for the whole trip. The next morning, when I tried to check the level, it was off the bottom of the dipstick. Cessna pulled the engine and replaced it in Honolulu, and I kissed the ground for my good luck. Had the leg been 15 hours...?

Oil temperature is another critical concern, and both too hot and too cold can be preludes to trouble. Every pilot knows to watch for high oil temps, but how many pilots have seen temperatures off the bottom of the gauge? A few years ago during an untanked winter delivery of a Cessna 400 (now Corvallis TT) from North Carolina to Geneva, Switzerland, I saw oil temps I couldn't believe. I was flying the leg from Bangor, Maine, to Goose Bay, Canada, in January, and the digital oil temp on the Garmin G1000 was showing me readings consistently between 60 and 70 degrees F. Most aircraft flight manuals prohibit even runups until oil temperature reaches 100 degrees F. At the time, OAT was about -40 degrees F, and I couldn't find any way to keep the oil warm. It turned out there had been a service bulletin issued by Continental requiring part of the cowling air intake to be blocked in extreme cold weather. That bulletin hadn't been complied with on my airplane.

On the surface, aircraft oil seems such a simple product, but my friend Ed Kaston, taught me differently. Every time I change oil on my Mooney, I replay Kaston's advice about the importance of proper lubrication in an aircraft engine. The alternative isn't even worth considering.


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