Oil Change: Hot or Cold?

[TiGeo]

Should probably try to come across better with your "sarcasm", because otherwise trying to make it sound like that afterwards sounds more like a backpedal, lol. Your comment of: "All that sticky high viscosity cold oil is hanging in the engine." in post 72 didn't sound anything close to sarcasm.

Wink wink wink-master. You really got me.

*GIANT ROLL EYE TO MAKE SURE ZEEOSIX UNDERSTANDS THIS IS SARCASM*

 

[ZeeOSix]

How you gonna prevent all that cold oil inside that hot engine not stick to parts in the top end?

 

[Faawrenchbndr]

Wow……..a crapload of “opinions” here

Some have merit, some I don’t believe in. But, I can respect others’ opinions.

 

[ATex7239]

Hot drain crowd: this is better.

 

[Gasbuggy]

when it's cold it, i change oil hot/warm so I'm warmer under the car. Opposite in the summer. I change it cold.

 

[zray1]

Hot drain crowd: this is better.

View attachment 202748

wow. No eye / face / full skin protection. Molten metal can and does explode if just a drop of water comes in contact…..

I’m in hot drain camp too. Reasons ? Who needs reasons ?

 

[camrydriver111]

This thread almost got me convinced to drain cold.

Then I saw this: draining hot for 1 hour drains the same amount of oil as draining cold for 6 hours!

 

[ZeeOSix]

Then I saw this: draining hot for 1 hour drains the same amount of oil as draining cold for 6 hours!

Of course, you'd have to drain much longer if done cold. The few times I've drained cold, I let it drain overnight, so at least 12-15 hours of draining.

 

[RyanY]

How you gonna prevent all that cold oil inside that hot engine not stick to parts in the top end?

^this
I have about a dozen jugs of Magnatec in my stash. Because cold temperatures increase the strength of magnetic fields, I drain it hot so the intelligent/magnetic molecules release from the various engine parts.

And the filter is easier to remove when the engine is hot.

 

[johnmyster]

I do it cold all the oil drained into the oil pan overnight

I did my first change the other weekend on our truck. It's an older diesel. I let it run for a few minutes while I put it on ramps, got supplies together, etc.

On restart I believe I counted to five before the oil pressure gauge moved. It seemed like an eternity.

My future changes will always be done directly after letting the car run for a few minutes. I want oil on all the parts, as much as I can help it.

 

[kschachn]

My future changes will always be done directly after letting the car run for a few minutes. I want oil on all the parts, as much as I can help it.

True but the oil never left. And even if the oil film thickness decreases it will happen faster with warm oil.

I’ve disassembled junkyard engines that were at least a decade old and oil is still covering all the surfaces.

 

[johnmyster]

True but the oil never left. And even if the oil film thickness decreases it will happen faster with warm oil.

I’ve disassembled junkyard engines that were at least a decade old and oil is still covering all the surfaces.

After a decade, did they incur a higher wear rate on the cold restart than during the rest of their lifecycle? Drained restarts are necessary, but are they not also less than desirable?

I never understand the logic. How does one get a cold engine? By letting a warm engine cool down. If the oil evacuates more when it's warm, it's not like it goes back there after cooling. You don't get to credit the cold state if it got there by cooling, parked, from a hot/warm state. Four possible scenarios and infinite intermediate variations:

1) Hot running engine. Park and immediately dump.
2) Hot running engine. Park until cold. Dump.
3) Cold running engine. Park and immediately dump.
4) Cold running engine. Park, wait, and dump.

So was the last "well lubricated" state hot, or cold? If there's any time a motor has the most chance/quantity of retained oil "sticking to" parts, it would be if it's been cold cranked and run for a short time, but not enough to get to temperature.

There is no way the period of startup idling with an empty oil system is good for the engine, or that the air getting pumped out of the system doesn't push oil off some important journal somewhere. How long is it okay to idle an engine without oil pressure before longevity of the motor is impacted in some way?

I get it. Film strength, adhesion, and viscosity are not one in the same, but there has to be some relationship.

EDIT: I guess my concern is irrelevant to the thread. I'm mostly concerned about the empty galleys that result from a filter change. (I am less concerned about the half quart of serviceable but dirty oil that is left behind.) The OP was about oil changes and didn't explicitly specify an accompanying filter change.

 

[kschachn]

It has nothing to do with film strength. And I’m also a little foggy on adhesion.

The rest of it I’m not really sure either. Galleys stay full when the oil is hot?

 

[ATex7239]

This thread almost got me convinced to drain cold.

Then I saw this: draining hot for 1 hour drains the same amount of oil as draining cold for 6 hours!

All these cold/hot and short/long drain videos do for me is reinforce my practice of cold drains 10 to 15 minutes. Not a single video has convinced me otherwise yet and this one is no exception. There was no difference at 15 minutes and additional 150ml (5oz/.15qt) is insignificant.

 

[ZeeOSix]

I did my first change the other weekend on our truck. It's an older diesel. I let it run for a few minutes while I put it on ramps, got supplies together, etc.

On restart I believe I counted to five before the oil pressure gauge moved. It seemed like an eternity.

My future changes will always be done directly after letting the car run for a few minutes. I want oil on all the parts, as much as I can help it.

It took a while to build oil pressure because you changed the oil and filter. It's going to do that regardless if the oil is change hot, warm or cold.

 

[ZeeOSix]

EDIT: I guess my concern is irrelevant to the thread. I'm mostly concerned about the empty galleys that result from a filter change. (I am less concerned about the half quart of serviceable but dirty oil that is left behind.) The OP was about oil changes and didn't explicitly specify an accompanying filter change.

Any time the oil filer is removed, the galleries can drain out, regardless of the oil temperature. There is nothing you can do about that. One thing you can do is pre-fill the oil filter as much as possible. Or figure out how to crank the engine without it starting to prime the oiling system. I pre-fill the filter and fire it up, which cuts the time down to see the oil pressure. Not worried about it beyond that.

 

[malibuguy79]

Of course, you'd have to drain much longer if done cold. The few times I've drained cold, I let it drain overnight, so at least 12-15 hours of draining.

aint nobody got time fo dat

 

[barryh]

I do it while the engine is running to make it exciting

With certain Vauxhall models, for added excitement the valve clearances were done with the engine running, just the job while you wait for all the oil to drain out.

 

[ZeeOSix]

aint nobody got time fo dat

Depends how you do it. The few times I did a cold drain, I didn't have to use the vehicle for awhile, so I dropped the drain plug and let it drain for a day. Didn't change anything in my daily schedule ... had another vehicle to drive.

 

[ZeeOSix]

There is no way the period of startup idling with an empty oil system is good for the engine, or that the air getting pumped out of the system doesn't push oil off some important journal somewhere. How long is it okay to idle an engine without oil pressure before longevity of the motor is impacted in some way?

A lot longer than 5 seconds or less that it takes to obtain oil pressure, which indicates the oiling system has oil flowing through it.