Oil Chage- Drain it hot or cold?

[Frankie]

I've always heard hot, and have always done it that way. I pull into the driveway after a good 15 minute run on the freeway, then let it drain for an hour. I also remove the filter during the draining which always pukes a little more out.

A mechanic friend claims that doing it cold is actually better because pretty much all the oil is in the pan after the engine has had hours to cool.

Sure would be easier to do it cold- less chance of a burn too-

What do you guys think?

 

[Ken2]

Hot. The oil carries out more contaminants. Allowing the oil to cool allows the contaminants to settle to the bottom of the pan, and there they'll stay. I feel that the amount of hot old oil remaining in the engine is completely insignificant after the oil drain slows to a drip.

Ken

 

[jeepzj]

I drain it hot as well after sitting for a few minutes. I first remove the oil filter then remove the drain plug. When it starts to come to a drip I pour in a full quart of el cheapo oil to try to flush out some of the remaining contaminants from the pan.

 

[Cutehumor]

quote:

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Originally posted by jeepzj:
I drain it hot as well after sitting for a few minutes. I first remove the oil filter then remove the drain plug. When it starts to come to a drip I pour in a full quart of el cheapo oil to try to flush out some of the remaining contaminants from the pan.

---

I drain hot but I do oil filter last. some cars you have no choice. a chevy cavalier/pontiac sunfire oil filter is in the back of the engine. major burn marks on my forearm just trying to take it off. pouring in cheap oil is fine to flush out old crap but for uoa purposes

 

[Frankie]

Originally posted by Ken2:
[QB] Allowing the oil to cool allows the contaminants to settle to the bottom of the pan, and there they'll stay.

Ken- Doesn't that old adage imply that there really are "contaminants" in the oil not picked up by the filter that will actually "settle"? I would think any metals (normally detected at concentrations of ppm's in the used oil analysis) would stay suspended in the oil at least for 12-24 hours.

Don't get me wrong though- I'll probably continue to drain it hot-if for no other reason that the "contaminants" would come out better with faster flowing hot oil.

[ March 02, 2004, 05:53 PM: Message edited by: Frankie ]

 

[JohnnyO]

I try to do it warm, not cold but not so hot that I burn myself. I think you get more out when it's warm-to-hot and thinner.

 

[Patman]

I drain it both hot and cold, if that makes sense. In other words I begin the draining process when it's super hot, but I leave it draining for up to two hours sometimes, so the engine cools right down by the time I'm done, and I make sure to get a lot more oil out this way.

 

[DEWFPO]

Did you ever try to drain oil when it was cold. It takes a lllooonnngggg time to get it all out. It will drip forever when cold. Besides, the hot oil still has a lot of stuff in suspension that hasn't settled to the bottom of the pan yet.

Hot/warm is the only way to go. IMHO

DEWFPO

[ March 02, 2004, 10:34 PM: Message edited by: DEWFPO ]

 

[labman]

I drain hot, but have been known to let it drain overnight. Just make sure you don't have to go anywhere the first thing in the morning.

 

[SteveD2]

I do it hot and only let it drip until I get the filter changed. This way there is still some of the old oil left in the engine to help with the dry start while the oil filter is being filled. No offense to your "mechanic friend", but the vast majority of mechanics that I've talked to/heard about know absolutely nothing about oil, even though they think they are an expert...

 

[Rick in PA]

Some like it hot. I do. The hotter the better. Watching that hot oil come gushing out of the crankcase gives me a nice warm fuzzy feeling.

It's an old habit I started after my brother and I rebuilt a motor decades ago. The motor had SAE 30 oil in it and we ran it up good and hot then dumped the oil. That 30 weight came out of the motor like a racehorse taking a ... ah never mind.

I've found it handy to use a short piece of heater hose that fits snuggly over the oil drain plug hex as a "handle" to remove the hot plug. And nitrile gloves, of course.

 

[RavenTai]

IIRC from school piston engines oil is supposed to be changed hot

I used to change them hot, but not the Toyota, I will be changing it cold as it has a horizontal filter (really want to fix that) that has to come out the top and by the time it cools most of the oil has drained out of the filter making much less mess at change time

I guess I could get real anal and drain it hot leave the plug out until it cools and then pull the filter but to much time for little return

 

[jeepzj]

quote:

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Originally posted by Cutehumor:

quote:

---

Originally posted by jeepzj:
I drain it hot as well after sitting for a few minutes. I first remove the oil filter then remove the drain plug. When it starts to come to a drip I pour in a full quart of el cheapo oil to try to flush out some of the remaining contaminants from the pan.

---

I drain hot but I do oil filter last. some cars you have no choice. a chevy cavalier/pontiac sunfire oil filter is in the back of the engine. major burn marks on my forearm just trying to take it off. pouring in cheap oil is fine to flush out old crap but for uoa purposes

---

I see nothing wrong with pouring in a full quart of oil to flush even with UOA tests. The sample I take for my used oil analysis is 3-5 seconds after I pull the plug. I pour in the quart of oil at the point right before it starts to drip....I already have my sample.

 

[jafo]

Seems to be easier if I loosen the oil filter when it's cold.I then warm it up for a couple minutes before draining.

 

[TC]

If you're in a rush, drain it cold. That way you know most of the old oil is already in the sump, and will mostly be removed.

Otherwise, certainly a long, thorough drain when hot is best (once it drips slowly, I figure that's good enough). From a 1973 Petersen's General Auto Repair Guide I have:

"It's advisable to drain the crankcase only after the engine has reached normal operating temperature. The benefit of draining is, to a large extent, lost if the crankcase is drained when cold, as some of the suspended contaminants will cling to the sides of the engine block and oil pan and will not drain out readily with cold, slow-moving oil."

There's an increased solvency effect I would think as well, like how warm water washes greasy hands better than cold water. Also, a recently-run engine has stirred up some amount of particulates on the sump bottom, and they'll drain out before they can resettle.

 

[Patman]

quote:

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I see nothing wrong with pouring in a full quart of oil to flush even with UOA tests. The sample I take for my used oil analysis is 3-5 seconds after I pull the plug.

---

You want to get your sample more from the middle of the draining process though, so it's better if you wait about 30-60 seconds after pulling the plug.

 

[widman]

Should always be hot. It will drain faster and take more contaminants out. Evven transmission and differencial oils. As I write this we are draining the two differencials, trans, and transfer case on my Toyota PU.
Caution when leaving overnight or several hours to try to get the last drop out....... The dust that can blow in from around the engine is more serious a problem than the drops of oil that might be left.