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cbriggs1978
Newbie


Joined: 02 Sep 2018
Posts: 29



PostPosted: Wed Oct 30, 2019 9:40 pm    Post subject: oil change - draining oil "cold" Reply with quote

Evening

Just got myself all set to do my first oil change on the 996. Simple question, is there any big advantage to warming the engine and draining oil hot rather than draining whilst cold but leaving overnight?

Just for curiosity!

Thanks

Chris
 
  
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kurlykris
Magny-Cours


Joined: 30 Jun 2014
Posts: 2573
Location: Warwickshire


PostPosted: Wed Oct 30, 2019 10:00 pm    Post subject: Reply with quote

I would say yes there is, get the engine warm, but not hot, before draining the oil.
If you think about it agitating the oil and the detritus sitting in the sump and around the engine will help it come out in the old oil, this is why oil samples should always be taken mid way through draining the oil Thumb
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Norfolk & Idea
Albert Park


Joined: 15 Jan 2016
Posts: 1584
Location: South Yorkshire


PostPosted: Thu Oct 31, 2019 5:15 am    Post subject: Reply with quote

I wouldn't bother warming it up. If i'd just come back from a drive, fair enough. But if I'd time, I'd just leave it to drain.
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Griffter
Spa-Francorchamps


Joined: 22 May 2016
Posts: 368



PostPosted: Thu Oct 31, 2019 10:04 am    Post subject: Reply with quote

One of the advantages of hot oil is that the viscosity is lower so it should flow out more easily/quickly. But IMHO if you can leave it draining overnight that’ll be fine.
 
  
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angry
Montreal


Joined: 30 Sep 2008
Posts: 613
Location: East sussex


PostPosted: Thu Oct 31, 2019 4:55 pm    Post subject: Reply with quote

kurlykris wrote:
I would say yes there is, get the engine warm, but not hot, before draining the oil.
If you think about it agitating the oil and the detritus sitting in the sump and around the engine will help it come out in the old oil, this is why oil samples should always be taken mid way through draining the oil Thumb


What he said, ive always done engine warm.
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GMG
Nürburgring


Joined: 07 Jan 2018
Posts: 463
Location: Devon


PostPosted: Thu Oct 31, 2019 5:42 pm    Post subject: Reply with quote

...hot or cold doesn't matter provided you allow time for a decent drain and is far less important than regular oil changes !

Put it this way...I would rather have a cold oil change once a year than a hot change once per two years!!
 
  
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7584
Location: Brighton


PostPosted: Thu Oct 31, 2019 7:54 pm    Post subject: Reply with quote

A long drain is better than hot i would say .. lets face it , if the car is at operating temps then the oil is 90 degrees .. you try to get the bung out at that temp and your going to get burnt .

I tend to have the cars about 50 degrees when i drain them , a road test first .. check some items and by the time its up in the air then im guessing thats about the temp .

You Can Not get all the oil out on an oil change .. you will always have approx 1.5 ltrs left in the engine .. this is due to the design im afraid .. oil gets trapped in places that only an engine strip will remove .

Best way .. leave it draining overnight .. you will get the maximum out that way .
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cbriggs1978
Newbie


Joined: 02 Sep 2018
Posts: 29



PostPosted: Thu Oct 31, 2019 8:01 pm    Post subject: Reply with quote

thanks for the input, getting it warm to mobilise any ***** into the oil before draining makes sense in my small brain!

I think I will take a little of everything you say, drive it, drain it, leave it overnight!

Regards

Chris
 
  
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infrasilver
Fast & Furious
Fast & Furious


Joined: 04 Oct 2010
Posts: 8502
Location: East Midlands

2001 Porsche 996 Targa

PostPosted: Sun Nov 03, 2019 3:36 pm    Post subject: Reply with quote

I do both but it depends on the circumstances. If its already in the garage I will drain it cold and leave it overnight and is my preferred method.

My logic is if it is cold, all the oil that can drain to the sump is already there, running the engine distributes the oil all over the engine again and you won't get as much old oil out as a cold drain over night.
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GMG
Nürburgring


Joined: 07 Jan 2018
Posts: 463
Location: Devon


PostPosted: Mon Nov 04, 2019 6:43 am    Post subject: Reply with quote

...totally agree; best method in my opinion.
 
  
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kas750
Shanghai


Joined: 31 Mar 2013
Posts: 4593
Location: Chorley lancashire

2006 Porsche 911

PostPosted: Mon Nov 04, 2019 6:54 am    Post subject: Reply with quote

infrasilver wrote:


My logic is if it is cold, all the oil that can drain to the sump is already there, running the engine distributes the oil all over the engine again and you won't get as much old oil out as a cold drain over night.

Spot on Thumb
 
  
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C4Silver
Spa-Francorchamps


Joined: 14 Aug 2019
Posts: 273



PostPosted: Mon Nov 04, 2019 3:32 pm    Post subject: Reply with quote

Well, if some one had told me that I’d have laughed in their face........ reading it though makes perfect sense ? Starting it up flings all the oil around the engine and whilst the particles will be suspended in the oil, of which 1.5 litres remains, the cold Oil will surely have the debris sat at the bottom of the pan which will be removed when the plug is taken out ?

In the case of pure unadulterated love and affection you could always rinse and repeat ? Just to squeeze every last drop out..... it’s always handy if you have an old diesel to use the nearly new oil in ?
 
  
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skinny_monkey
Nürburgring


Joined: 16 Sep 2014
Posts: 464



PostPosted: Mon Nov 04, 2019 10:59 pm    Post subject: Reply with quote

Why not both. Get it hot and then drain it overnight?
 
  
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C4Silver
Spa-Francorchamps


Joined: 14 Aug 2019
Posts: 273



PostPosted: Mon Nov 04, 2019 11:10 pm    Post subject: Reply with quote

Dunno, seems again like a logical suggestion but in my head I’m thinking about the hot engine cooling from hot to ambient temps with no oil in,

Or as suggested from 50 degrees would seem even more plausible, the point I was trying to make was that draining an engine cold actually seems pointless, but when you I think about it !!!


All the crud is there in the sump just waiting to be drained.

Which ever route, regular changes with good quality oil.
 
  
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7584
Location: Brighton


PostPosted: Tue Nov 05, 2019 8:28 pm    Post subject: Reply with quote

There is no crud as such .. that's back in the ford escort days of poor quality fuel . oil and how engines ran .. usually rich !

we used oil thinning additives back then on an oil change to break all the crud down .

Oil comes out pretty clean on Porsches compared to the old days .. i was there then lol .

If we wanted to be technical .. oil expands when hot so in essence it occupies a larger area ..

If at operating temp and then drained and left overnight you would get fractionally more oil out due to the expansion of the oil .

I feel we are into milliliters at this point though .

Cold or hot and you will get the most out via an over night drain .. you will still have the best part of 1.5 ltrs still in the engine though .

To be perfect .. change the oil .. run it to operating temps then change it again to dilute what's in there with fresh .. dump it and refill with new again .. probably down to less than a 5% mix of old oil with new .

getting silly at this point though and rather expensive Smile
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skinny_monkey
Nürburgring


Joined: 16 Sep 2014
Posts: 464



PostPosted: Tue Nov 05, 2019 10:15 pm    Post subject: Reply with quote

C4Silver wrote:
Dunno, seems again like a logical suggestion but in my head I’m thinking about the hot engine cooling from hot to ambient temps with no oil in


When you turn the engine off, the oil will start cooling and dropping back to the sump. Your engine doesn't know or care if the sump plug is fitted or not.
 
  
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MisterCorn
Dijon


Joined: 08 Jan 2011
Posts: 7315
Location: Nottingham, England

2004 Porsche 996 Turbo

PostPosted: Wed Nov 06, 2019 8:25 am    Post subject: Reply with quote

I'm with Infrasilver. If the car has been sat for some time, all that is going to get back to the sump will have drained there, you are then just draining the sump.
If the engine is warm/hot or has run recently, then you are also waiting for all of the oil which will drain back from the rest of the engine to get back to the sump, so it will take longer.

I usually drain mine cold and leave it until it is dripping slowly. No point waiting all night for the last 10ml when there is still 1.5l sat in the engine.

If the oil is dropped first, by the time the rest of the parts required for a service have been done it is time to put the plug back in.

MC
 
  
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C4Silver
Spa-Francorchamps


Joined: 14 Aug 2019
Posts: 273



PostPosted: Wed Nov 06, 2019 8:40 am    Post subject: Reply with quote

skinny_monkey wrote:
C4Silver wrote:
Dunno, seems again like a logical suggestion but in my head I’m thinking about the hot engine cooling from hot to ambient temps with no oil in


When you turn the engine off, the oil will start cooling and dropping back to the sump. Your engine doesn't know or care if the sump plug is fitted or not.


I get that the engine doesn’t understand that there is no Oil in there, I’m guessing you can see from my posts that I don’t actually get the science behind the Oil expansion etc, my thinking was that from 90 degrees operating temps and cooling with no Oil in might be detrimental to the engines internals as the working parts contract to cold with 1.5 litres of oil in there as opposed to 9 ?

And I totally get the None overnight drain, why wait all night for a few drops when there’s still over a litre in there, the reasoning behind that is perfectly logical.
 
  
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skinny_monkey
Nürburgring


Joined: 16 Sep 2014
Posts: 464



PostPosted: Wed Nov 06, 2019 12:34 pm    Post subject: Reply with quote

C4Silver wrote:
skinny_monkey wrote:
C4Silver wrote:
Dunno, seems again like a logical suggestion but in my head I’m thinking about the hot engine cooling from hot to ambient temps with no oil in


When you turn the engine off, the oil will start cooling and dropping back to the sump. Your engine doesn't know or care if the sump plug is fitted or not.


I get that the engine doesn’t understand that there is no Oil in there, I’m guessing you can see from my posts that I don’t actually get the science behind the Oil expansion etc, my thinking was that from 90 degrees operating temps and cooling with no Oil in might be detrimental to the engines internals as the working parts contract to cold with 1.5 litres of oil in there as opposed to 9 ?

The working parts cooling won't be affected by anything, oil will start to drain down, leaving approx 1.5l around the engine. The remaining oil will either sit in the sump or drain out - either way, not doing anything with the engine. As soon as the engine stops turning, there's no oil pressure and so the oil is doing nothing with the working parts. The oil drains down and then engine cools in the same way except obviously, if you don't drain from hot, the engine takes longer to cool down as you have additional thermal mass in there.
Oil expansion, the volume occupied by a given mass of oil increases slightly with temperature (density decreases). So if you had 8l of cold oil in the sump, it might be 8.5l when it's hot.
 
  
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