Drain oil, hot or cold?

[SteveInMD]

One thing about free information is that everyone has their own opinion.

Isn't that the point of this web site?

 

[SkyPup]

We pour three liters of liquid nitrogen down the oil fill tube, open the oil drain bolt, tap the oil pan with a rubber hammer, and all the little broken pieces of oil come raining down out of the oil pan containing all the sediments frozen into them.....

 

[Doc_Bob]

We pour three liters of liquid nitrogen down the oil fill tube, open the oil drain bolt, tap the oil pan with a rubber hammer, and all the little broken pieces of oil come raining down out of the oil pan containing all the sediments frozen into them.....

Now, do you get your liquid nitrogen locally or do you have a internet supplier? Do you buy in bulk? Gallon? Quart? What are you paying for you liquid nitrogen? Do you pay road tax or do you buy offroad liquid nitrogen? Is it dyed or undyed?
Bob

 

[Doc_Bob]

Bob it's not strictly a matter of time or we would all be draining our oil cold. Oil is drained after the engine has warmed to help flush out any impurities, chips or the like that remain in the bottom of the oil pan that the oil filter didn't catch because they settled out of the oil.

Okay, now a fliter will do 10 microns? A red blood cell is 7 microns. I can handle any 10 micron particle left in my sump. My fingers are so "delicate" that I hate anything hurts my little fingers (ouchie!!!!!!!!) If the filter has not filtered a chip, I have bigger problems than hot or cold issues.

Bob

 

[Highbeam]

Say you have a heavier chip of something just floating around down there in the sump, maybe they keep getting picked up by the oil pickup screen and then dropped when you shut down. Wouldn't you want that out?

Have you ever changed the differential oil in your pickup after the initial 30000 miles or so of use? It has a magnet but also tons of sludge and chips setting on the bottom of the sump. I don't want my engine to look like that.

 

[RobJ]

Here's how I see it...

If you drain it cold it has had a long time to drain down into the oil pan from up in the motor, i.e., since it last ran.

If running your motor stirs up a bunch of sediment in your oil pan, you've got bigger problems to worry about than your oil temperature.

Me to. I use to drain hot, makes sence. But if you are using the sediment theory then now all that mixed in sediment is coating ALL your engine parts. Only way to get is all is let the oil drain out overnight. But then the engine cools and some of the oil will stay in so you still didn't get it all. With cold drain and let it sit for 15 minutes, the oil has already drained down from the engine into the pan. Now if you qare worried about sediments, then like mentioned you have bigger problems and maybe you should change your oil sooner. In the end 6-8 quarts of oil and a few ounces of bad...not much you can do.
But someone could suggest draining a cold engine BUT installing an oil heater to heat the oil then drain. Best of both I guess.

 

[Doc_Bob]

Say you have a heavier chip of something just floating around down there in the sump, maybe they keep getting picked up by the oil pickup screen and then dropped when you shut down. Wouldn't you want that out?

Have you ever changed the differential oil in your pickup after the initial 30000 miles or so of use? It has a magnet but also tons of sludge and chips setting on the bottom of the sump. I don't want my engine to look like that.

Very good points.
Bob

 

[RobJ]

Very good points.
Bob

A differential doesn't have a filter to take those out like an engine does. I have magnets on all my ATV's and I barely get anything on them. Just a little smudge of stuff. If there are heavy chips floating around then you probably are about to have bigger problems.

Really go to a shop that rebuilts engines and ask around. Any well maintained engine I rebuilt didn't have any sludge (basically dirt, carbon, etc) in the pan. But ones that didn't get regular PM would have a nice thick layer of this stuff. It would sort of feel like wet clay sticking together, dry in the middle, I could get it out in chunks. And believe me, once this stuff formed, hot oil did not break it down when the engine was running. Worst I've seen is when I took off the valve cover, you couldn't see the springs. It was caked in that bad.

 

[Highbeam]

I used the differential comparison to show that the sludge, chips, and goo can happen in an oil even though no failure has occured. That goop might have been filtered out from the engine oil if it ever got a chance to make it to the filter or it might just swim around in the sump. I have taken apart the oil pickup tube screens and found them packed with junk that was too big to make it to the filter (AMC304V8). If I can possibly get any junk out of the engine I don't want to miss that chance. If there isn't any junk since the filter is working so well and the maintenance excellent then great, no harm done.

I don't want to be burned so in answer to the original question: Freshly run and warm, not hot.

 

[Sully2]

Say you have a heavier chip of something just floating around down there in the sump, maybe they keep getting picked up by the oil pickup screen and then dropped when you shut down. Wouldn't you want that out?

Have you ever changed the differential oil in your pickup after the initial 30000 miles or so of use? It has a magnet but also tons of sludge and chips setting on the bottom of the sump. I don't want my engine to look like that.

But dont forget...the rear end isnt "force lubricated" and has "no filter" either!!! If you have any lube supply that is filtered...LMAO..even with an infamous FRAM filter...and your seeing that sort of stuff in your oil...then the filter has no "guts" in it and is nothing more than a metal can...