Change oil Hot or Cold?

[427Z06]

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One is only draining the oil (more oil than a short hot oil drain) from the pan...More dirty oil in the pan to be drained...less in the engine.

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But is the difference significant? A half hour after a hot drain, I doubt there's more than a half-cup of oil left in the engine, if even that.

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Cold oil flows freely..and with enough current to sweep away particulates that are no longer suspended (if any) in the oil.

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Easy for you to say, you live in Huntington Beach, CA. Imagine changing oil in the winter in Chicago. Assuming a typical 5w30, 17cSt @176°F, 168cSt @68°F, 570cSt @32°F.

And if you're taking a sample from the drain stream, you want the oil and contaminants well blended, like after a long drive.

 

[Quickbeam]

I agree. If the goal is to get as much as the old oil out as you can in the least amount of waiting time draining it cold is the way to go. It's when the dipstick reads it highest. A pan heater would be the hot setup.

 

[tenderloin]

427Z06

I agree there maybe only a few ounces difference. Is 8 oz significant? I doubt it. My point is how 'cold drains" are not even considered by many..when in fact it makes perfect sense. Now if one is in -20 degree weather and you happen to be changing oil under those conditions, I can see your point.

I would guess most oil changes are not done either anywhere near those temperatures or conditions..but then again, I live at the beach.

Btw Jan 1 and turn on your TV for the Rose Parade. We are having a cold spell here. Only 55 degrees at 9 AM. Even under these trying conditions, the cold oil flows from the pan like water from a hose.

 

[obbop]

Lukewarm!!!!!!!!!

 

[peterr]

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This is sooo hilarious. On a cold drain you are only draining the oil from the pan. It does easily drain out. The hot oil on shut off ends in the pan. It is so simple, yet years of "changing it hot" have clouded your minds. Stop and think for a second. One is only draining the oil (more oil than a short hot oil drain) from the pan. Cold oil flows freely..and with enough current to sweep away particulates that are no longer suspended (if any) in the oil.

More dirty oil in the pan to be drained...less in the engine.

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Yes it is hilarious. The insistence that cold oil flows just fine under all temperature conditions and that anyhow it would not matter in an 'oil change in sub 50 degree weather with the engine cold from the night before' because

"the vast majority of people haven't " had to do this.

Yeah the vast majority of the citizenry of Huntington Beach California, I guess.

Anyhow I am not doctrinaire about this. I don't think it makes a huge difference in how much oil you get out, but I do drain hot. The last oil change I did was at temperatures in Farenheit around 25 degrees. 5w30 does not "flows freely..and with enough current to sweep away particulates that are no longer suspended (if any) in the oil" as compared to hot.

It is supposed to be 28 degrees Farenheit here tonight. If my oil didn't have only 150 miles on it I would feel like draining it just to show the effect. But as a purely practical point when I drain oil hot it stops after 15 minutes. At 28 degrees I could leave it for hours, and I don't believe its current would wash out particulates in the bottom of the pan.

Anyhow, I am not really arguing the central principle. I don't contend that there is likely to be a huge benefit from changing hot or cold. However the assertions about cold oil flow and the lack of importance temperature plays in many people's environments are really just silly.

 

[427Z06]

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Btw Jan 1 and turn on your TV for the Rose Parade. We are having a cold spell here. Only 55 degrees at 9 AM. Even under these trying conditions, the cold oil flows from the pan like water from a hose.

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1:30 pm here: outside temp 53°F, my garage 58°F, the oil in my sumps 53°F.

 

[Patman]

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Btw Jan 1 and turn on your TV for the Rose Parade. We are having a cold spell here. Only 55 degrees at 9 AM.

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I know this is offtopic but I just find it funny that you guys are considering 55F to be cold, but here in Toronto it's almost 50F today and it is considered very warm for January 1st!

(normal high for Jan 1st is 30F)

 

[427Z06]

Yep Patman...have to actually keep the windows closed today since it's so cold here right now.

 

[Patman]

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Yep Patman...have to actually keep the windows closed today since it's so cold here right now.

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And I was just outside for a few minutes in a short sleeve shirt with no jacket on, so it's funny how our perspectives are different eh?

 

[Flat_H]

I changed my oil the other day when it was 35 outside. It wasn't too bad. I wish it were 55 outside today so I could go to the driving range and work on my iron shots.

Anyway, I still think you should drain the oil when it's at a normal operating temperatures in the engine.

 

[oli]

It appears that many people are overlooking the final step in an oil change. The final step is restarting the engine with a filter that is not full. I much prefer to start the engine while it is still hot and there is still the greatest amount of warm oil covering all moving parts.

 

[Leon]

There is absolutely no need to leave the oil plug out for more than a few minutes. An oil change for my civic means 3.3 lt (with filter) while after a rebuild it will need about 4 liters. There is 0.7 liters of oil inside the engine unless you shake the car and turn it upside down.

 

[GeorgeCLS]

The engine oil addives that hold particles in suspension are heat activated. The hotter the oil, the better the dispersion additives work. Thus changing the oil hot will enable significantly more suspended wear and contamination particles to be drained with each oil change. The cooler the oil is the more particulate settling will have occurred..

Hot oil changes over the long run will result in a significantly cleaner engine.
George Morrison, STLE CLS