Draining oil hot or cold questions?

[Artem]

Originally Posted By: 02SE
Back in my consumer car repair days, I did some experimentation with cold and hot oil drains. The cold drain invariably left more junk in the engine in every case. No matter how long it was left to drain. In one case up to a week with the drain plug out.

Seeing the results with my own eyes numerous times, in my own vehicles I always get the oil up to full operating temperature and make sure it stays there for awhile to make sure any junk is in suspension in the oil, before I drain the oil while it's still at full operating temperature.


Nice post. Thanks for sharing your personal experience.

 

[Artem]

Originally Posted By: 4WD


Using premium oils known for keeping engines clean is a great way to keep them draining well …


Well said.

 

[bbhero]

I think 4wd is right on about this... Running good oils known for helping keep a motor clean is the biggest part of the equation.

 

[Ducked]

6 pages on this very simple question with a bleeding obvious answer?

And I'm adding a post to it? We are all nuts.

Hot obviously. The official advice in this case makes sense.

Wear gloves if you don't like burning yourself with carcinogenic fluids.

 

[Artem]

Exactly. I strap a rubber glove on top of my Mechanix work gloves. Can't even feel the hot drain bolt. And once I pull the plug, I pull off the rubber glove and I'm clean and unburnt underneath.

 

[Nyogtha]

Originally Posted By: Artem
I know this question has been...

But I figured I'd include some, you know, PROOF, instead of just running my fingers on the iPhone screen again.

So I took the used oil from the last few oil changes I did on various cars and examined the contents that settled on the bottom of my clean gallon jugs from drinking water. I then proceeded to shake the oil until the bottom was clean and all settled contents were back in suspension again.

I marked the jugs with various test numbers for internal use and 24 hours later, I poured out the oil into another clean water gallon and these are the pics of the bottom of the gallons. Enjoy

This last one is from yours truly and my 2014 Mazda 3. Clean drain pan, warm / hot oil instantly poured into the gallon and sealed to prevent contamination. I then went back under the car to mess with the oil filter, etc in case any dirt would fall into the pan from the oil filter and ruin my test.

OEM Mazda filter was cleaning this oil for 4,000 miles.





As you can see from my short test, in my honest opinion, if you drain the oil COLD, you take a chance of leaving all this junk sitting on the bottom of the block and it instantly contaminates the new oil & oil filter.

From my experience servicing HUNDREDS of cars, some oil pans have idiotic drain hole designs which prevents ALL the oil from draining. This leaves a good bit of the heavy particles sitting in the bottom with a cup or two of old oil.

This issue is further compounded in cars that get serviced on a lift, where you're not able to tilt the car in a way to aid draining of more old oil. So even more [censored] gets left behind in the block.

P.s. The next portion of my test is to examine how much more stuff settles from the oil, having left the majority of the big stuff behind in gallons #1. If more stuff settles, I'll repeat the test a third time (I've got plenty of clean gallon jugs) until the old nasty oil doesn't leave behind any settled particles, if that's even possible. Stay tuned...

Without similar pics drained at ambient temperature to show a difference / differential, this shows only one case.

If I do not exceed the varnish solubility of my oil over a OCI, then it won't settle / plate out. If varnish is settling out at ambient temperature, it's doing it every day when I'm done driving for the day - then going back into solution presumably as soon as the circulating oil reaches operating temperature again?

If the heaviest particles are settling out overnight, they must have been too small for the oil filter to capture in the first place, so the harm done is what? If the heaviest oil particles are then re-suspended by fresh oil, they will either be captured by the fresh oil filter, or not, and the question remains why the prior oil filter didn't capture them. If they're smaller than the range to do damage already, so what?

FWIW, Stokes flow equations for pumped forced flow through a filter are not the same as simple gravity settling.

I see both sides of the coin in detail.

 

[Ducked]

Originally Posted By: Nyogtha


If the heaviest particles are settling out overnight, they must have been too small for the oil filter to capture in the first place, so the harm done is what? If the heaviest oil particles are then re-suspended by fresh oil, they will either be captured by the fresh oil filter, or not, and the question remains why the prior oil filter didn't capture them. If they're smaller than the range to do damage already, so what?


This assumes that there is (a)a lower size threshold below which there is no damage, (b)a lower size threshold below which there is no filtration, and that (c) b is the same as or less than a.

I doubt any of these assumptions are valid and supported by evidence.

 

[Nyogtha]

Well, if your filter isn't targeting the size range of 15 to 25 microns the old GM study stated caused the most damage, what are you targeting?

BTW, that's my target, purchasing filters with 94+% efficiency at 20 microns.

Your doubts?

 

[Ducked]

Originally Posted By: Nyogtha
Well, if your filter isn't targeting the size range of 15 to 25 microns the old GM study stated caused the most damage, what are you targeting?

BTW, that's my target, purchasing filters with 94+% efficiency at 20 microns.

Your doubts?


My doubts are as above. I doubt that particles (especially metal particles, of which I seem to have a lot) below 20 microns do no damage, and I don't know the performance of my oil filter, though I MIGHT be able to find out what performance is claimed.

Even if you are correct, you are only considering the wear effects of the particulate material carried over into the fresh oil, but it is well known that both metallic and organic contaminants have catalytic "seeding" effects which are likely to accelerate the deterioration of the fresh fill.

It therefore makes sense to get as much of it out as possible, and that is best accomplished by draining it hot directly after a run.

Which is where we came in.

 

[Nyogtha]

Can you please be more specific on a technical basis what exactly you doubt about 15 to 25 microns being the most damaging particle sizes specifically with respect to the GM study? Rather than just being extremely broad & vague that this has never been accomplished.

This is the first I've seen metallic particles thought of as "seed"particles for additional metal to agglomerate on. Can you explain that mechanism?

I have no dispute carbon particulate agglomerates. However, if it is of size to do damage, it will pass to the filter first. If it is not, it is not of the size to do damage.

 

[Ducked]

Originally Posted By: Nyogtha
you please be more specific on a technical basis what exactly you doubt about 15 to 25 microns being the most damaging particle sizes specifically with respect to the GM study?


No. I don't have time to search for alternative studies right now, but I have seen them. They may have been from sources with a vested interest in flogging secondary/bypass filtration systems, but, as I said, even if you're correct, where's the payback in leaving stuff smaller than 25 microns in your sump when you could get it out?

Originally Posted By: Nyogtha
This is the first I've seen metallic particles thought of as "seed"particles for additional metal to agglomerate on. Can you explain that mechanism?


No. I don't feel the need to explain your mis-representation of what I said, but since you mention it, I can't rule it out. Removal of non-ferrous particles by magnetic separation suggests that weak agglomeration probably does happen, though I doubt its very significant in this context.

Metal catalysis of oil oxidation is probably significant, however, as is auto-catalysis by varnish precursors. There is no lower size limit on this, and in fact smaller particles, having a greater surface area, are likely to be more damaging.

http://www.machinerylubrication.com/Read/998/varnish-formation

"Table 2 demonstrates the relationship between the presence of metal catalysts and water versus oil oxidation as measured by the acid number (AN)."

That's in turbine oil, which differs from engine oil, but it seems likely similar mechanisms operate there.

Taken to its logical limit, your complete faith that your oil filter will remove all unpleasantness from your oil would mean you would only ever have to change your filter, and in fact bypass filter enthusiasts do sometimes claim:-

"Oil doesn't wear out, it just gets dirty"

Nice story, except it isn't true.

Oil wears out AND it gets dirty.

 

[dlundblad]

Various manuals say to drain different fluids hot while the contaminants are in suspension.

 

[Nyogtha]

Ducked, I'd love to see you use the quote feature hefe to show I stated an oil filter will remove all oil contaminants, but we both know you can't.

TBN and the need for such does not exist as particulate but is in solution. Comprehend solution vs. duspension?

Since you choose not to present a technical counter yo the GM study, we'll leave it as flat-earth extrapolation, At this point I doubt you ever read even a summary of that study. You choosing to indicate my posts had anything about filtration only being required shows your choice to deviate from facts for your own satisfaction.

As far as metal catalysing varnish, what do you reckon your whole engine's lubricated surfaces are made of, and ignores the sump is the lowest temperature spot in sn engine without an oil cooler. Are you saying your engine has so much metal particulate that that particulate significantly increases the surface area of metal oil is in contact with in your engine? Do you believe that occurs in all engines?

If you look back at my initial post, you'll probably see me and some others speaking about no hot surfaces to contact while under the car. I and some others see that as an advantage.

 

[Nyogtha]

Originally Posted By: dlundblad
Various manuals say to drain different fluids hot while the contaminants are in suspension.


Not so in the owner's manual for any vehicle I've ever owned, or my parents ownned.

 

[Patman]

I'm surprised nobody has mentioned this yet but the reason why I change the oil hot is because I'm always taking a sample of the oil to send off for analysis and we've been told by various sources that it's a better representation of the condition of the oil if you collect it hot compared to collecting it cold.

 

[Danh]

Originally Posted By: Nyogtha
Originally Posted By: dlundblad
Various manuals say to drain different fluids hot while the contaminants are in suspension.


Not so in the owner's manual for any vehicle I've ever owned, or my parents ownned.


Take a look at any Honda/Acura owner's manual: they say to drain at normal operating temperature. Honda is unusual in that it actually provides oil change instructions in the manual; maybe that's why you haven't seen it elsewhere.

 

[StevieC]

Originally Posted By: Patman
I'm surprised nobody has mentioned this yet but the reason why I change the oil hot is because I'm always taking a sample of the oil to send off for analysis and we've been told by various sources that it's a better representation of the condition of the oil if you collect it hot compared to collecting it cold.


I was going to mention it but didn't want to get told that used oil analysis are useless.

 

[Ducked]

Originally Posted By: Nyogtha
Ducked, I'd love to see you use the quote feature hefe to show I stated an oil filter will remove all oil contaminants, but we both know you can't.


And didn't. I said "unpleasantness", by which I meant damaging contaminants, which is, as far as I can tell, pretty much by definition what you are saying when you repeatedly refer to stuff being below the size threshold for damage because it passes the filter.

Originally Posted By: Nyogtha
TBN and the need for such does not exist as particulate but is in solution. Comprehend solution vs. duspension?


"duspension"? Should that be DUHspension?

No, sorry. No idea what you're talking about.

You can't be saying there's no interaction between the particulate phase and the liquid phase, because that would be absurd.

I assume AN is mentioned in the reference I linked to because it is an indication of oil oxidation, due to the formation of organic acids, and this is catalysed by the presence of metals.

Originally Posted By: Nyogtha
Since you choose not to present a technical counter yo the GM study, we'll leave it as flat-earth extrapolation, At this point I doubt you ever read even a summary of that study.


Doubt away. I'll try and contain my indifference

Originally Posted By: Nyogtha
You choosing to indicate my posts had anything about filtration only being required shows your choice to deviate from facts for your own satisfaction.


An extrapolation, as I think I made quite clear


Originally Posted By: Nyogtha
As far as metal catalysing varnish, what do you reckon your whole engine's lubricated surfaces are made of, and ignores the sump is the lowest temperature spot in sn engine without an oil cooler. Are you saying your engine has so much metal particulate that that particulate significantly increases the surface area of metal oil is in contact with in your engine? Do you believe that occurs in all engines?


Dunno. Wouldn't be particularly surprised if all those questions had affirmative answers.

Originally Posted By: Nyogtha
If you look back at my initial post, you'll probably see me and some others speaking about no hot surfaces to contact while under the car. I and some others see that as an advantage.


Well it is. Just not a very big one. First time I burn myself doing an oil change I'll change my mind and just do it warm. I can't see any reason to do it cold.

 

[Nyogtha]

Wow, now even personalizing over a typo. Clearly your lack of ability to carry out a technical discussion is shown quite clearly if you think AN or TBN are filterable. You see where oil MSDS speak of a small amount of additional oil added for additive solubility? Those additive wear out and in a combusti9n engine from byproducts of combustion far outweigh any other source of incom8ng acid, but you want to be stuck on turbines.

As far as being burned during an oil change I did have that happen as a teenager on an exhaust component, so been there done that.

Keep on keeping on that particulate in your oil significantly increases the oil wetted metal surface area - while I really foubt that. The metal isn't a porous honeycomb for the oil.

Ignore on! What a great feature I've found this to be here!

 

[Ducked]

http://www.machinerylubrication.com/Read/30165/oil-oxidation-stages

Wear metals (c) have the potential to cause or accelerate oxidation reactions by means of metal ions in copper, cobalt, chromium, iron and other transition metals. Thus, not only does oxidation have the ability to create wear debris, but wear debris can cycle back to promote further oxidation.

"Another example of oxidation propagation would be peroxy radicals reacting with additional hydrocarbons to produce hydroperoxides and more alkyl radicals."