Oil Change: Hot or Cold?

[ZeeOSix]

Nature doing nature things and the little buggers will be blended fairly quickly.

Blackstone labs used to ask for their samples to be taken hot after taking it around the block a few times, but they removed that from their instructions.

Here is the link from 2021, and their current link. Excerpting here for easier reading.

2021
"Run the engine before you take the sample to get the oil at operating temperature (driving about 20 minutes should do it). Getting the oil up to operating temperature should help cook out any moisture or fuel build-up from the last time you drove. Then let the engine cool down a bit before you pull the sample. We don’t want you to get burned, and we don’t want to melt the tubing if you’re using a quick-draw pump to pull the sample."

Gas & Diesel Sampling | Blackstone Laboratories

web.archive.org

Current
"It doesn’t matter if the oil is cold or hot when you take a sample. Just try not to start the engine immediately prior to sampling. Even if you do though, it’s not a big deal. Just let us know."

Gas & Diesel Oil Sampling Procedure | Blackstone Laboratories

Gas or diesel engine oil sampling is easy with Blackstone's free oil analysis kit. Here's how to do it!

www.blackstone-labs.com

I'm mildly curious about what caused them to change their sampling procedures, knowing them its probably backed by data.

They probably changed it to hot or cold because they think it doesn't matter as long as the sample is taken mid-drain point as their following statement says:

"If you’re changing the oil, try to pull your sample from the middle of the drain. The first oil out might have some dirt from around the drain plug. If you wait till the end, you might not have enough oil left to fill the bottle."

Although, IMO if it was done shortly after warm or hot engine shutdown vs cold there might be slightly more suspended particles that the oil filter couldn't filter out. If someone was doing a particle count with their usual UOA to say compare filter efficiency impact on oil cleanliness, I'd suggest doing a warm/hot drain for the UAO. Without an added particle count on the UOA, it wouldn't matter if the sample was taken hot or cold. A normal Blackstone UOA doesn't include an ISO particle count. If Blackstone was more detailed in their instructions, they should probably say if you want a particle count of the UOA, then the sample should be taken warm/hot shortly after engine shutdown.

 

[ZeeOSix]

This will sound very BITOG - but one could argue if most of the oil is in the pan - and some particles settle overnight - just pulling the plug cold will dump the bottom particles and all the rest of the oil (with cold viscosity) sweeps the bottom …
In other words - there is likely no bad way compared to not changing the oil … Do what works for you …

Hard to say. But I’ve always done cold drains and my engines have always been fine. Spotless even. My opinion it doesn’t matter either way… So no need to waste gas, time, and contend with hot oil is the way I see it.

There was someone here who posted in a similar thread that he always drained oil cold, and at some point he had to remove the oil pan on the engine and he said the bottom of the pan was spotless. It's in one of the 100s of "drain oil hot or cold" threads, lol.

 

[Speedy3861]

Don't really know, I take 4 quarts to the dealer, have a trusted tech who removes the shield under the engine(actually replaces all the fasteners too) changes the oil using the Honda filter. I imagine the oil, is hot/warm when he does this. He cleans up the mess the filter makes, probably using brake clean and wiping and a rag, replaces the drain washer and actually uses a torque wrench to tighten the drain plug, I know, I've watched him work. Never had a drip. I always bring a dozen donuts for him and his team.
When I do UOA's, I use the pump from Blackstone with the oil hot. At 76 with Siatica, my OCI's are no longer DIY. It's good to have reasonable priced, quality help. When I did DIY, always hot or at least very warm, never really thought about it.

 

[LouC]

When I had to change the trans oil on my 07 Jeep in the dead of winter (not bitter cold but 32*F) there was no way it was pumping out of the trans pan cold. I had to heat the pan with a heat gun to get it to flow. Worked pretty well, I was able to suck out about 1/2 of what was in the pan before cracking it loose. Still makes a mess but not as big of a mess. The primary filter had clogged and the trans would not go into gear so I couldn't drive it.

 

[burbguy82]

sweeps the bottom

That makes a bunch of sense as well. If it would work that way.

 

[Chief119]

Oil drains best at 152 degree F, not any hotter or colder. There is your answer.

 

[4WD]

Oil drains best at 152 degree F, not any hotter or colder. There is your answer.

C’mon man - Even a ZF transmission has a range of temps

 

[TiGeo]

Hot is the way, I can't believe folks do this stone cold and expect the same drain "cleanliness".

 

[ZeeOSix]

Hot is the way, I can't believe folks do this stone cold and expect the same drain "cleanliness".

There is no proof that draining the oil hot leaves the sump "cleaner". See posts 59, 60 & 62. How much oil is drained out is based on the drain temperature and how long it's left to drain. Of course, when the oil is hot it will drain faster, but if someone pulled the drain plug and let it drain overnight, then just as much oil will drain out.

 

[TiGeo]

There is no proof that draining the oil hot leaves the sump "cleaner". See posts 59, 60 & 62.

Cool story, I'll continue to feed off of paranoia in a non-data driven approach to this question thank you very much. Warm/hot > cold...weirdos!

 

[ZeeOSix]

Cool story, I'll continue to feed off of paranoia in a non-data driven approach to this question thank you very much. Warm/hot > cold...weirdos!

LoL ... paranoia? Exactly how is draining the oil hot leading to a "cleaner" drain if the total oil drain volume is the same? Obviously, more drain time is needed if the sump is drained when cold.

 

[TiGeo]

LoL ... paranoia? Exactly how is draining the oil hot leading to a "cleaner" drain if the total oil drain volume is the same?

All that sticky high viscosity cold oil is hanging in the engine. I hear doing it cold decreases engine life so that '99 Camry will only go to 389,975 vs. 400K! I'll take that 10,025 extra miles than you very much.

 

[ZeeOSix]

All that sticky high viscosity cold oil is hanging in the engine. I hear doing it cold decreases engine life so that '99 Camry will only go to 389,975 vs. 400K! I'll take that 10,025 extra miles than you very much.

Read post 59 again. You do realize that when a hot engine is shut off, all that hot oil drains down into the sump as much as physically possible. If the sump is drained after the oil cools down to room temperature without starting the engine again, you just need to extend the drain time to get a full drain volume.

Now if the engine is cold, and someone fired it up for 2 minutes to move the car for some reason, then drained the engine, there would be cold oil in the top end, if that's what you're referring too. But even in that case, if the drain time was over night it would still provide a complete drain. You have to use a drain time that's right for the drain conditions.

 

[4WD]

Or …

 

[JeffKeryk]

You're supposed to change it?

 

[nickaluch]

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

 

[RazorsEdge]

I've done it both ways,makes no difference.

 

[TiGeo]

Read post 59 again. You do realize that when a hot engine is shut off, all that hot oil drains down into the sump as much as physically possible. If the sump is drained after the oil cools down to room temperature without starting the engine again, you just need to extend the drain time to get a full drain volume.

Now if the engine is cold, and someone fired it up for 2 minutes to move the car for some reason, then drained the engine, there would be cold oil in the top end, if that's what you're referring too. But even in that case, if the drain time was over night it would still provide a complete drain. You have to use a drain time that's right for the drain conditions.

You seem to be missing my sarcasm....yes, I get how this all works. I prefer warm/hot oil b/c I can drain it quickly vs. a longer wait as you state in the post.

 

[buster]

Scolding hot with your bare hands.

 

[ZeeOSix]

You seem to be missing my sarcasm....yes, I get how this all works.

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.