Oil change: Hot or Cold?

Do you get the oil warmed up before doing an oil change?

  • Hot

    Votes: 39 88.6%

  • Cold

    Votes: 1 2.3%

  • Either

    Votes: 3 6.8%

  • Whatever the mechanic says

    Votes: 1 2.3%
  • Total voters
    44
A

asicer

Touchdown! Greaser!
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asicer
Seems like most of the time, I've seen folks run the engine and get the oil up to temperature before changing the oil but I've also seen more than a few do it with everything cold.

Is changing cold oil really all that evil?
 
When it's over eighty, I don't think it makes much difference. I've changed it cold and hot, but I don't make any effort one way or the other.
 
asicer said:
Is changing cold oil really all that evil?
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In my experience when straying from the OEM's recommended practices you end up on the shorter end of the stick. In the case of cold oil changes, over time you will end up with more contaminants and deposits built up in the engine than if you drained it within the 15 to 30 minutes after engine operation as recommended. While warm oil does drain faster, the main purpose of draining with warm/hot oil is to remove the contaminants that only become suspended in the oil during engine operation.
 
If the engine has been run enough to get up to temperature, it's stirred up as much silt/debris/sludge/etc as possible, so that stuff will drain out when you drain the oil. Are you removing an additional gram of crud from the engine vs a cold drain? An additional .001 gram? I dunno, but it has to have some impact.
 
Warm. Not scalding anything but still flows. Well enough to drain quickly
 
asicer said:
...Is changing cold oil really all that evil?
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EvilEagle said:
I always drain it after flying, come back the next day and put the fresh oil in. Good excuse to fly and easy cleanup.
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if anyone would know, it'd be evileagle


I've done warm and cold. either way I let it drain overnight
 
I have mostly done it warm, but I have done it cold many times at work.
At work some crankcases hold 44 qts and use giant filters. Doing those hot is dangerous from getting burnt by the giant oil filter and when removing the large drain plug.

I always fly the plane first and then drain the oil as soon as I get back to the hangar. Like in 10 minutes after I get back because I do want that hot oil to drain fast.
I will let it drain for maybe an hour. Then finish the job.

I never let anything drain over night anymore.

Years ago I drained a commercial air compressor of oil and let it drain while I went to dinner.
When I came back to the shop, I had tire changes on my mind and forgot I was in the middle of a oil change.
Turned that compressor on and within 30 seconds or so it was squealing and the pump was damaged.

So I always finish a oil change with no work in between.
 
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An aircraft with the cowl off in the middle of a oil change is hard to forget.
But a truck or car sitting around with no oil is very dangerous because of it getting started and moved is much greater than your aircraft with the cowl removed.
IMO those last few drops of old oil is not going to hurt your engine.
I feel so un easy when it is sitting there with a empty crankcase.
 
I would argue that the truck or car sitting around with no oil is not dangerous at all because it's highly unlikely to kill you.

Some planes don't require the cowl to be removed. There was a local guy who flew to a nearby airport for an oil change. Drained the oil, went off to do something else, came back, went to fly home, and augered in after takeoff.
 
I fly it, then decowl and drain hot. Let it sit overnight, pull and inspect the screens, wash the engine with mineral spirits, and refill.
 
GeorgeC said:
I would argue that the truck or car sitting around with no oil is not dangerous at all because it's highly unlikely to kill you.

Some planes don't require the cowl to be removed. There was a local guy who flew to a nearby airport for an oil change. Drained the oil, went off to do something else, came back, went to fly home, and augered in after takeoff.
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Wow!
Dangerous to your checkbook...lol
 
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If you are using AD oil the contaminates are held in suspension by (no kidding) tails on the additive molecules. Larger particles should be filtered out by the oil filter. That leaves the bits that are to big/heavy for the AD oil to suspend and to small for the paper element to capture.

Those mid size particles generally don't weigh enough to settle out unless left alone for a long, long time. It really doesn't have much to do with the temps (unless you're talking sub zero) but the agitation of the oil to re-emulsify the particulates that have settled out.

While heat will improve viscosity, heat is not the real reason you want to drain after a flight. The real reason is that the particulates are still in the oil and can be drained out. You could drain an engine 'cold' and then wash the oil pan through the drain hole (with a tube etc) to get the settled out particles and have a much cleaner oil pan.
 
I like the oil quite warm after an engine run. Some of my intent is to have any sediment that may have settled in the sump to be stirred up and taken out with the fast flowing hot oil.

As others have noted, I finish the oil change so as to not get distracted doing something else. When I have to leave it in the middle of an change (very seldom) I will put a note over the ignition switches ...
 
Not just the temp, but a half hour flight should get more stuff stirred up and likely to drain, no?

Hell, my 20-50 would take 4 days to drain out cold.
 
When I leave mine overnight, the cowling is open, the drain tube is hooked up and draining into the bucket. If I came in the next day, closed the cowl, removed the tube and bucket then went flying without putting oil in it.... I deserve that one.
 
Half the time, I did mine hot. The other half, I open the drain plug and go home. Come back the next day and finish up.
 
Define cold. If it's been sitting for an hour and the oil is cool to the touch, the sediment is still mostly mixed in it. If it's been sitting overnight or longer, that's plenty of time for the sediment to fall to the bottom of the sump.
 
TCABM said:
Last time I walked away from an oil change led to a catastrophic failure. That Honda lawnmower never stood a chance.
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I've known a few family members with old pushmowers that never changed the oil over a 20 year period...so do we really need oil changes? :popcorn:
 
Rarefied said:
I've known a few family members with old pushmowers that never changed the oil over a 20 year period...so do we really need oil changes? :popcorn:
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Funny you should ask. The lawnmower was shipped in household goods, so the oil had to be drained. Nine months later when I went to mow for the first time at our place in Colorado I had completely forgotten about it having been drained.
 
asicer said:
Seems like most of the time, I've seen folks run the engine and get the oil up to temperature before changing the oil
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I've always thought that the perfect solution would be to drain a cupful cold to eliminate any sediment that may have settled to the bottom, then warm up and change hot.
 
geneseib said:
I've always thought that the perfect solution would be to drain a cupful cold to eliminate any sediment that may have settled to the bottom, then warm up and change hot.
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What is that a solution to?
 
It is better to change when hot for the reasons listed above. So my official recommendation is hot. However in the “do as I say not as I do” category…

In all the vehicles I’ve owned and all the oil changes I’ve done, I’ve pretty much always done them cold because I don’t like dealing with hot oil, and normally it’s just more effort to go run/warm up something before the oil change.

I’ve never had a failure or problem that I could attribute to that. Really engines have been pretty reliable for me.

Just changing the oil has you better off than anyone who doesn’t, which is a frighteningly large number of people.
 
geneseib said:
I've always thought that the perfect solution would be to drain a cupful cold to eliminate any sediment that may have settled to the bottom, then warm up and change hot.
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The problem with that is the sediment won't drain, which is the whole point of changing the oil when it's hot to begin with.
 
Paul New, Tennessee Aircraft Services, recommends allowing a day or more to settle prior to changing the oil. The idea being to allow as much oil as possible to return to the sump. He does also recommend running the engine heater, if so equipped to reduce the viscosity. He has quite impressive credentials.
 
robin ardoin said:
Paul New, Tennessee Aircraft Services, recommends allowing a day or more to settle prior to changing the oil. The idea being to allow as much oil as possible to return to the sump. He does also recommend running the engine heater, if so equipped to reduce the viscosity. He has quite impressive credentials.
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A day to settle? Wouldn’t allowing that same day for draining accomplish the same thing, and even better if starting with hot oil?
 
I fly at least 45 minutes to warm the oil and burn off any condensation. Then I uncowl and then go get lunch or a coffee.

By the time I get back, everything is still warm, but not too hot to work on. Perfect time to change the oil.
 
I'm a terribly slow airplane maintainer. It's also kind of a pain to pull it out, file a flight plan, and fly it for a few minutes, then push it back in. Getting the cowling of a 182 is not a trivial task, and by the time I get everything off I'm happy to let it drain, catch a sample, and let it go overnight.

The goal of an oil change is not to get every single molecule of contaminant out, but to get the majority of contaminants out each time while repeating on a regular basis. I'm sure one way is better than another, but not by such a substantial margin that it likely effects motor longevity or safety.
 
Half Fast said:
A day to settle? Wouldn’t allowing that same day for draining accomplish the same thing, and even better if starting with hot oil?
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Yes, it would; that question was brought up in the 210 maintenance course I attended. Paul’s view was that he prefers allowing all of the oil to drain from the passages/prop governor (if applicable) and draining it overnight would accomplish that with the risk of forgetting to replace the drain plug. In their shop they feel it is safer to complete the job in a short block time vs overnight to reduce error chances. By warming the oil with an engine heater they get excellent removal of most of the oil and particulates.
 
robin ardoin said:
Paul New, Tennessee Aircraft Services, recommends allowing a day or more to settle prior to changing the oil. The idea being to allow as much oil as possible to return to the sump. He does also recommend running the engine heater, if so equipped to reduce the viscosity. He has quite impressive credentials.
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I knew Paul when he started out as a avionics guy in the early 80's and his dad Joe had the salvage shop in West TN.
 
robin ardoin said:
Yes, it would; that question was brought up in the 210 maintenance course I attended. Paul’s view was that he prefers allowing all of the oil to drain from the passages/prop governor (if applicable) and draining it overnight would accomplish that with the risk of forgetting to replace the drain plug. In their shop they feel it is safer to complete the job in a short block time vs overnight to reduce error chances. By warming the oil with an engine heater they get excellent removal of most of the oil and particulates.
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How do they know? I have the utmost respect for Paul, but I'm curious how they measured this.

I've always used my preheater to warm the oil before dumping it. To drain my oil I need to reach past the exhaust pipe, so running the engine for any period of time is not much of an option. I like to think the thinner oil will flow better, causing more 'junk' to be removed from the pan. I honestly don't know. I'm betting all of the methods work pretty much the same. The major point of changing the oil is to remove the dissolved acid build-up from combustion, which probably occurs the same either way. The filter is for particulates.
 
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