Hot or Cold oil change?

[RazorsEdge]

I've done it both ways, doesn't make a difference on how long a vehicle lasts in the long run.

Worry about something more important, some of you take this abit too far.

 

[SR5]

Well I did my very first cold oil change today and it went well. By cold I'm talking about 30C (86F) in my part of the world. At that temperature the synthetic 10W30 drained out easy and well. It looked to be the same volume as usual. The cold oil filter was much easier to remove, not as tight and no burning from the nearby exhaust system.

I'm not worried about the quality of the job. The oil filter is there to remove larger contaminants, while the dispersants and detergents in the add pack are there to make sure the smaller contaminants remain in suspension and don't settle out when the car is parked overnight.

Sure back in the day of Group I & II 20W50, hot made sense, and it still does in a cold climate or if the oil has been pushed too far. But for Group III & IV synthetics in a mild climate and with good cold flow properties and not pushed too far in terms of distance, I felt fine doing a cold oil change.

Thanks for all the input.

 

[ZeeOSix]

Originally Posted by Jackson_Slugger
I drain hot because I think contaminates drop down to the pan when warm and I think there is a better overall flushing.


If there are any contaminants that fall out of suspention and drop down and collect in the pan, that happens every time the engine is ran and then shut off. If those contaminates always stay at the bottom of the pan even if the engine is ran (ie, settled contaminates not stirred up and resuspended) then they probably won't drain out regardless if the oil is drained hot or cold.

I typically drain when the oil is pretty warm (20-30 mim after shutdown) and let it drain for an hour while I'm changing the filter and checking over other things. But the few times I've drained it cold, I let it drain over night (with filter removed too) so I get the same amount out as if drained warm. When drained cold, it's only the pan that's draining since all oil in the upper end has already drained to the pan.

 

[Mad_Hatter]

Originally Posted by ZeeOSix
Originally Posted by Jackson_Slugger
I drain hot because I think contaminates drop down to the pan when warm and I think there is a better overall flushing.


If there are any contaminants that fall out of suspention and drop down and collect in the pan, that happens every time the engine is ran and then shut off. If those contaminates always stay at the bottom of the pan even if the engine is ran (ie, settled contaminates not stirred up and resuspended) then they probably won't drain out regardless if the oil is drained hot or cold.

... and over time that's the sludge that forms in the pan. If you've ever cleaned out your pan you know that stuff can be pretty hardy and doesn't easily move/go anywhere. The smaller 5~10 micron size particles that do the most damage in an engine are likely still being held in suspension, hot or cold, and drained out the next oil change. Anything large enough to not be held in suspension by the lubes chemistry has either been filtered out or will spend the rest of it's existence at the bottom of the pan.

To me the hot/cold question is a solution in need of a problem....

 

[PowerSurge]

A warm engine (sitting for about 30 minutes) is the best of both worlds. It still flows out fast, it's had more time to drip down into the sump, and you won't burn yourself on a hot exhaust pipe, etc.

 

[demarpaint]

Originally Posted by PowerSurge
A warm engine (sitting for about 30 minutes) is the best of both worlds. It still flows out fast, it's had more time to drip down into the sump, and you won't burn yourself on a hot exhaust pipe, etc.

That works fine and imo is the best of both worlds. By the time I get things set up and ready to change the oil, the engine has cooled enough to safely handle the oil change. And as I mentioned earlier if things are a little too hot to handle I always have my rubber gloves.

 

[FCD]

On both of my cars the drain plug and the oil filter are very close to the exhaust, i don't fancy getting scolded on a hot exhaust so i do it cold or at most lukewarm.

 

[SteveSRT8]

I feel like you are engaging in wishful thinking if you believe that sludge on the bottom of your oil pan will not get stirred up at higher rpms as hot oil flows over it.

 

[RooflessVW]

Originally Posted by SteveSRT8
I feel like you are engaging in wishful thinking if you believe that sludge on the bottom of your oil pan will not get stirred up at higher rpms as hot oil flows over it.

And it is easily proven. Do a hot drain into a light-colored pan/jug. Wait until the oil is cool and empty the pan/jug.

What's left is what sits on the bottom of your oil pan, and it isn't nothing.

 

[FCD]

I feel like a lot of people do not realize that the combustion byproducts do not settle at the bottom of the pan when you shut the engine off.
Oils are designed to keep all that in suspension and not let it settle, because if you did allow them to settle they would rather quickly start forming sludge deposits.

 

[Mad_Hatter]

Originally Posted by SteveSRT8
I feel like you are engaging in wishful thinking if you believe that sludge on the bottom of your oil pan will not get stirred up at higher rpms as hot oil flows over it.

I've never found sludge in any filter in over 160k miles, never had a plugged oil gallery (low pressure) and when I did the valve covers a couple years back I didn't notice ANY sludge..a little varnish but no sludge. Then again I've religiously changed the oil on time between 4~5k miles from day one. So for me it's not wishful thinking, it's fact...but I suppose it's possible in your car it works differently....

 

[Luftmasse]

I dont think it matters much since you got the New oil filter on. The left overs are not much anyways.

 

[jqgz]

The Subaru takes about 4.5 quarts. I change it cold, pour in 1/2 quart with the drain valve still open to flush anything sitting in the pan out, then close it and fill. I am of the mindset cold is better. Everything has dripped down. I also put the car into clear flood mode (hold gas pedal to floor) and crank it for 3 seconds after refilling. This gets oil moving a bit so I don't get a dry start.

 

[SteveSRT8]

Originally Posted by rooflessVW
Originally Posted by SteveSRT8
I feel like you are engaging in wishful thinking if you believe that sludge on the bottom of your oil pan will not get stirred up at higher rpms as hot oil flows over it.

And it is easily proven. Do a hot drain into a light-colored pan/jug. Wait until the oil is cool and empty the pan/jug.

What's left is what sits on the bottom of your oil pan, and it isn't nothing.


Exactly. We often put used oil out in jugs for disposal, sometimes they sit a while.

When they do, there is a layer of crud on the bottom. Seems to me some of those suspended contaminants do indeed settle out of the oil. Why would anyone imagine they don't???

 

[350Rocket]

Originally Posted by Duffyjr
Originally Posted by PimTac
On the other hand, draining it hot also means stuff is suspended better so you might be getting more stuff out that would otherwise build up inside.

I have to ask where do the contaminants go when the oil is cold? As the engine cools and the oil drains back to the pan do the contaminants get left behind. Just trying to wrap my head around this because I don't change my oil any longer so when I take it to the quick lube the oil is warm but when I leave it with my mech it's usually the night before so I know he's not letting it warm up so if this is an issue I might consider going back to the quick lube.




Mind you, I'm a bit old school so this might not apply as much as it did 45 years ago with thicker oil. It was the thinking then that stuff settled in the pan. In that era engines ran dirty and sludge was a battle.

This is a interesting point that SR5 is trying to bring up. I do the change hot because of beliefs that are decades old. Maybe they don't apply anymore? In either case I still drain the oil hot as I've done for decades. Old habit I guess.

I don't think it's old school. It's just better practice. Unfortunately it won't happen leaving it overnight at your mechanic, part of why I will always do my own oil changes. I prefer to change it after at least a half an hour drive and let it drain for half an hour. It'll be fine if you don't, but still better to do it.

 

[philipp10]

One could argue that if I start the car to heat the oil, I've just pumped all the contaminates that were on the bottom of the pan from sitting overnight to the top of the engine. Then I would have to wait hours for it to all settle back to the bottom? I don't know.....just a thoery.

 

[Cerjed]

I try to freeze my car first before doing an oil change. The ice sheet underneath makes it easy to slide in and out under the car. It's currently due and I'm waiting for a snowstorm so I can get it done soon.

But seriously, I've always done it on a cold engine during summer months. By the time I change the filter, it is done draining and nothing is coming out anymore. Hot or cold, I don't think it really matters in the long run, as long as you use quality oil, quality filter and stick to a reasonable interval.

 

[RazorsEdge]

The last time I changed oil in the Ford Escape, I changed it hot and let it drain overnight.

I even used Royal Purple HMX which is double the price of Supertech oil.

Ask me if I care,

 

[JohnnyJohnson]

View attachment 37416

I try to freeze my car first before doing an oil change. The ice sheet underneath makes it easy to slide in and out under the car. It's currently due and I'm waiting for a snowstorm so I can get it done soon.

But seriously, I've always done it on a cold engine during summer months. By the time I change the filter, it is done draining and nothing is coming out anymore. Hot or cold, I don't think it really matters in the long run, as long as you use quality oil, quality filter and stick to a reasonable interval.

That definitely looks like the OCI weather I plan on missing!

 

[AutoMechanic]

I try to do it warm but cold sometimes if we haven’t driven it the whole day. Definitely not hot nothing worse than being burnt by hot oil which has happened to me a few times lol.