[prkaye]

I'll be doing my first oil change soon. I believe the recommendation is to do the change after a flight, so the oil is warm and will flow-out better. Weather may make a flight on the day I want to do my change impractical. How long a ground-idle would be sufficient to warm the oil enough for an oil change? Or would my oil sump preheater warm it up enough? I'm on mineral oil right now.

 

[Sid Lambert]

One of the reasons to run the engine before changing the oil is so that any solid particles that may have settled can become suspended in the oil. I would run the engine for a while before draining. I have done this without flying (weather) and felt the oil should have been warmer so I try to avoid just a ground run.

 

[JonJay]

I have done it both ways...

It is easier when the oil is warm and cleaner as it drains from the filter much better. (I pierce the filter and drain it before I remove it.) I usually let it sit over night to drain, but not always.
The school of thought on doing it cold is that the oil has had time to collect in the sump. It drains much, much more slowly obviously.

 

[DEWATSON]

Draining the oil at operating temperature is best. All of the contaminants are in suspension and flow out of the engine when you drain the oil. It would really be best to fly the airplane before you do the oil change. The engine should be heat soaked for the best results.

 

[Flybuddy2]

I never bought the theory of drain while warm/hot. Do those particles now become unsuspended when cold and remain in the pan when drained cold?? I don't think so, if they did, what would happen when warming up and they are between suspended and unsuspended? If the weather is warm/hot, just drain without running. If you start on the ground you're now running dirty oil throughout the engine that'll take a long time to drain back down to the pan and unless you let it drain for a very long time you won't be as thorough in old oil removal. To test this theory, take 2 pans of drained (dirty) oil, one hot and one cold, tip over and let drain for several hours. Wipe the bottom of both pans with clean towel and you'll see no discernible difference.
I submit that the only reason for hot oil draining is that it flows faster.

 

[Neal@F14]

If it's cold and I don't want to run the engine or fly before an oil change, then I'll plug in my Tanis pre-heater to warm up the oil

 

[aerhed]

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I never bought the theory of drain while warm/hot. Do those particles now become unsuspended when cold and remain in the pan when drained cold?? I don't think so, if they did, what would happen when warming up and they are between suspended and unsuspended? If the weather is warm/hot, just drain without running. If you start on the ground you're now running dirty oil throughout the engine that'll take a long time to drain back down to the pan and unless you let it drain for a very long time you won't be as thorough in old oil removal. To test this theory, take 2 pans of drained (dirty) oil, one hot and one cold, tip over and let drain for several hours. Wipe the bottom of both pans with clean towel and you'll see no discernible difference.
I submit that the only reason for hot oil draining is that it flows faster.

My thinking also. When I can, I just let it drain overnight. Usually much neater changing a cold filter also. One more bonus: No hot engine burns.

 

[RVadmirer]

Oil Analysis

If you are going to do an oil analysis it is recommended to fly first. See this from Blackstone:

Fly the aircraft before you take the sample to get the oil at operating temperature. How long does it take? We suggest, at minimum, flying around the pattern a couple of times. Getting the oil up to operating temp before taking the sample should help eliminate any normal moisture or fuel build-up.

 

[Sid Lambert]

The heat has nothing to do with keeping the dirt suspended, the agitation is whats doing the job. Warm oil just drains faster.

Since you are wanting to play Bill Nye, try this. Take some warm, recently run but dirty oil from say a lawn mower and put it in a clear mason jar. Let it sit for a few weeks then use a siphon to pull the oil from the top. See what's left in the bottom.

I never bought the theory of drain while warm/hot. Do those particles now become unsuspended when cold and remain in the pan when drained cold?? I don't think so, if they did, what would happen when warming up and they are between suspended and unsuspended? If the weather is warm/hot, just drain without running. If you start on the ground you're now running dirty oil throughout the engine that'll take a long time to drain back down to the pan and unless you let it drain for a very long time you won't be as thorough in old oil removal. To test this theory, take 2 pans of drained (dirty) oil, one hot and one cold, tip over and let drain for several hours. Wipe the bottom of both pans with clean towel and you'll see no discernible difference.
I submit that the only reason for hot oil draining is that it flows faster.