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Thread: O200 oil temps

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    Junior Member
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    Default O200 oil temps

    This summer I recently acquired a sport cub with the Dynon 180 which provides a lot of engine temperature info. Recent flying at OAT of less than 45 degrees the engine oil temp will only get up to around 120 degrees. The plane has cowl vents and an oil cooler. My understanding is that oil temps of 180-200 are recommended to evaporate moisture in the oil. Should I be concerned?

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    Senior Member 40m's Avatar
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    Default Re: O200 oil temps

    Quote Originally Posted by DonL View Post
    This summer I recently acquired a sport cub with the Dynon 180 which provides a lot of engine temperature info. Recent flying at OAT of less than 45 degrees the engine oil temp will only get up to around 120 degrees. The plane has cowl vents and an oil cooler. My understanding is that oil temps of 180-200 are recommended to evaporate moisture in the oil. Should I be concerned?
    Small Continentals ~100 above outside temp is common. I would cover with tape opening in baffle to oil cooler then part of the cooler face as outside temps dropped. Also changed oil during winter more often.

  3. #3
    Member stroutmail's Avatar
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    Default Re: O200 oil temps

    No doubt that evaporation rate of water out of the oil is better at 180F than 120-140F. But, getting the oil hot does not necessarily remove moisture from the crankcase. And the amound of time the oil is "hot" is important. 220F for a short time may not remove any more water from the oil than 140F for a long time.

    Hot air holds more moisture..the air in the crankcase is most certainly saturated. And, it is the moisture that condenses when the oil and air in the crankcase cools that remains in the crankcase and causes damage. Best calculation is about 30 "drops" of water (as water vapor) are held in the hot air inside the crankcase.

    There are some who address this by opening the oil fill cap to allow the hot moist air to escape with cooler drier air entering the crankcase by backflow thru the breather after shutdown. Some have even introduced inert nitrogen into the crankcase. And there are recirculating devices that remove moisture with dessicant.

    On a cold day. I can get the oil temp up to 160-180F by increasing load by climbing at Vx. And, I preheat my engine before takeoff so oil is above 70F on start. At shutdown, I open the oil fill for about 30-60 minutes as I secure the plane and hangar. I use CamGuard additive and change oil often.

    I have used duct tape to cover air inlets on race cars, but duct tape (even the aluminized type) makes me uncomfortable in a plane..I would prefer a means that is mechanically attached like a plate over the air inlet to the scat hose.

    I would use engine oil analysis to provide needed info as to oil drain interval and operating oil temps. I think you will find that high quality oil drained at 25 hours or less with oil temp in the 120-140 F range will prove to be acceptable.

    Running at excessive low temps may affect the formation of lead deposits on valves, so CHT and EGT along with oil temp should all be considered.
    Last edited by stroutmail; 12-26-2019 at 01:35 PM.

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