Draining oil hot or cold questions?
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Originally Posted By: bbhero
I agree jakewells. Ohh did you find some oil at a low everyday price around you to buy??
cleaned out a dollar general of there peak hm 10w40 BOGO. the local aap has valvoline vr1 20w50 for 1.25 per qt.
I agree jakewells. Ohh did you find some oil at a low everyday price around you to buy??
cleaned out a dollar general of there peak hm 10w40 BOGO. the local aap has valvoline vr1 20w50 for 1.25 per qt.
Here's what I Do..and did tonight.
With temps at 42° outside, start my Prizm in the driveway, let it Idle for about 2 minutes, cruise through the neighborhood @ 30 mph for approximately 2 miles till operating temperature.
I then jump on the Highway for about 4 miles @ 65-75 mph. I then pull into my garage, grab my 14mm box-end, loosen bolt and slowly unscrew by hand till around 2 turns remaining.
I'll then "Spin the Bolt" dropping it onto the screen on my Drain pan opening, while the hot Oil drains out. If there's any oil spill at all, it's about 2-4 drops of splatter. If I'm in no hurry, I'll let it drain overnight like it is as I'm typing this, it's dripping away.
This might seem like Overkill, but it's how "I" do it....
With temps at 42° outside, start my Prizm in the driveway, let it Idle for about 2 minutes, cruise through the neighborhood @ 30 mph for approximately 2 miles till operating temperature.
I then jump on the Highway for about 4 miles @ 65-75 mph. I then pull into my garage, grab my 14mm box-end, loosen bolt and slowly unscrew by hand till around 2 turns remaining.
I'll then "Spin the Bolt" dropping it onto the screen on my Drain pan opening, while the hot Oil drains out. If there's any oil spill at all, it's about 2-4 drops of splatter. If I'm in no hurry, I'll let it drain overnight like it is as I'm typing this, it's dripping away.
This might seem like Overkill, but it's how "I" do it....
Originally Posted By: CR94
Originally Posted By: Nyogtha
^^^ Agreed! Unless your contaminants are large enough to be seen by the naked eye and fished out with your fingers as nuggets . . . in which case you have other issues. ...
There's a wide range between too small to be seen and "nuggets."
So you get my point?
I can PM you Stokes regime settling equations so hou can calculate for yourself. I cranked through a lot if those back in college. Drag forces from the fluid medium solid particles are suspended in exert significant resistance to gravity in small particle sizes.
Originally Posted By: Nyogtha
^^^ Agreed! Unless your contaminants are large enough to be seen by the naked eye and fished out with your fingers as nuggets . . . in which case you have other issues. ...
There's a wide range between too small to be seen and "nuggets."
So you get my point?
I can PM you Stokes regime settling equations so hou can calculate for yourself. I cranked through a lot if those back in college. Drag forces from the fluid medium solid particles are suspended in exert significant resistance to gravity in small particle sizes.
You aren't just trying to remove suspended solids.
There's stuff like Varnish whose properties and solubility are temperature dependent.
Drain dead cold (overnight), and whatever solids are dropping will have dropped. Whatever temperature soluble component are dropped, and the viscous boundary layer (think Reynolds number here) that's lining the bottom of the sump will be holding whatever it's holding ready to partially load the next oil change.
Hot maximises the amount of oil that drains in the average 10 minutes or so, has the most solubility for temperature dependent effects, and Reynolds number is higher meaning more turbulence to carry stuff out.
Haven't read many owners manuals that advocate a cold drain.
There's stuff like Varnish whose properties and solubility are temperature dependent.
Drain dead cold (overnight), and whatever solids are dropping will have dropped. Whatever temperature soluble component are dropped, and the viscous boundary layer (think Reynolds number here) that's lining the bottom of the sump will be holding whatever it's holding ready to partially load the next oil change.
Hot maximises the amount of oil that drains in the average 10 minutes or so, has the most solubility for temperature dependent effects, and Reynolds number is higher meaning more turbulence to carry stuff out.
Haven't read many owners manuals that advocate a cold drain.
4wd
$50 site donor 2026
I’m not on the cold and overnight side of the fence ~ but when drained a few minutes after engine shutdown ~ hot or warm seem pretty close when it’s already agitated and hardly laminar flow out the pan … 3 of my drains are at the rear and my ramps are 9” tall …
I have used my extra half quart or some clearance oil a few times down the top when the plug was out … this oil looked very clean … I’ll do that on the Cruze at my next change w/ 100k (for grins) … it gets accused of being a little oil monster …
(Straight down drain)
I’m just not going to burn myself over the difference … (and I’m pretty HSE driven from job) …
I have used my extra half quart or some clearance oil a few times down the top when the plug was out … this oil looked very clean … I’ll do that on the Cruze at my next change w/ 100k (for grins) … it gets accused of being a little oil monster …
(Straight down drain)
I’m just not going to burn myself over the difference … (and I’m pretty HSE driven from job) …
+1 Ed
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...
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...
Originally Posted By: Artem
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.
That's a good demonstration. Hopefully it will convince all mambie-pambies the importance of draining hot.
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.
That's a good demonstration. Hopefully it will convince all mambie-pambies the importance of draining hot.
Originally Posted By: SHOZ
Good luck getting all the oil out of an engine.
That's not the point of this thread though... we all know you can't get it all out... but it doesn't hurt to try.
A did a mini test once. I drained the oil with the car level until it was slowly dripping (most would have called it a day already). I then raised the front end literally 6 inches (tires didn't even leave the ground) and measured how much more oil came out. A got almost a FULL party sized cup of oil out.
I did this test when I first got my Mazda 3 to see if it's worth it for me to raise the front end or if the drain hole is designed well enough to drain most of the oil out.
Good luck getting all the oil out of an engine.
That's not the point of this thread though... we all know you can't get it all out... but it doesn't hurt to try.
A did a mini test once. I drained the oil with the car level until it was slowly dripping (most would have called it a day already). I then raised the front end literally 6 inches (tires didn't even leave the ground) and measured how much more oil came out. A got almost a FULL party sized cup of oil out.
I did this test when I first got my Mazda 3 to see if it's worth it for me to raise the front end or if the drain hole is designed well enough to drain most of the oil out.
Originally Posted By: SHOZ
Good luck getting all the oil out of an engine.
Exactly not the point...the bit that's left will be holding ALL the junk that settles out instead of being mixed in the oil.
(not all really, but a lot more than if it's mixed before draining...the viscous layer on the floor of the sump will be laminar, not turbulent, and will leave any and all settled deposits sitting on the floor)
Good luck getting all the oil out of an engine.
Exactly not the point...the bit that's left will be holding ALL the junk that settles out instead of being mixed in the oil.
(not all really, but a lot more than if it's mixed before draining...the viscous layer on the floor of the sump will be laminar, not turbulent, and will leave any and all settled deposits sitting on the floor)
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.
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.
Originally Posted By: Shannow
... the viscous layer on the floor of the sump will be laminar, not turbulent, and will leave any and all settled deposits sitting on the floor)
Even when drained hot, it might not be turbulent very far from the drain opening, although obviously farther than if cold.
... the viscous layer on the floor of the sump will be laminar, not turbulent, and will leave any and all settled deposits sitting on the floor)
Even when drained hot, it might not be turbulent very far from the drain opening, although obviously farther than if cold.
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4wd
$50 site donor 2026
I’ve never seen chunks come from an engine in 40 years of changing oil …
And how cold/warm depends on where you live … warm is my pick for road vehicles … but with a dead battery I changed the boat oil cold today … that cool oil was very thin … and in 5 seconds I’m looking at the bottom of a plastic bottle where 10w30 had sit for 18 months …
Using premium oils known for keeping engines clean is a great way to keep them draining well …
And how cold/warm depends on where you live … warm is my pick for road vehicles … but with a dead battery I changed the boat oil cold today … that cool oil was very thin … and in 5 seconds I’m looking at the bottom of a plastic bottle where 10w30 had sit for 18 months …
Using premium oils known for keeping engines clean is a great way to keep them draining well …
Originally Posted By: SHOZ
If you are going to do a test then you should also drain some cold and see what settles out of it too.
I suspect that if most of the big stuff remains in the engine, less stuff will settle in my gallon jugs, if any at all, since the settled stuff remained in the engine. Makes sense to me.
If you are going to do a test then you should also drain some cold and see what settles out of it too.
I suspect that if most of the big stuff remains in the engine, less stuff will settle in my gallon jugs, if any at all, since the settled stuff remained in the engine. Makes sense to me.
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