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ballcock
Sepang


Joined: 21 Jul 2008
Posts: 2943
Location: Dublin

1996 Porsche 993 Carrera 2

PostPosted: Wed Jan 30, 2019 7:52 am    Post subject: Hot Oil Pressure Difference After Service Reply with quote

Just a quick note for those who may wish to increase their idle oil pressure once the engine is warm.
My 3.4 was running just above a bar with the oil that was in the car when I purchased it. I can’t know for sure but I believe it had 5W30 a few months before I bought it.
I’ve just had the car serviced with Millers 10W50 , and hot idle is a full bar higher, at just under two bars, the engine definitely runs sweeter and quieter from first turn of the key, but this may be due to the plug and coil pack change also done during the service.

(NOTE, for those of you who are happy with one bar (you know who you are!) I’m not suggesting this will affect logivity etc, but it certainly makes me feel better!)
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'96 Iris C2 vario manual coupe, Koni FZD's/M033's RSR's and HID's.
‘98 Ocean blue 996 C2 Tip pressed into daily service.

Ex '83 W460 LWB G Wagen updated with OM602 engine and 6 speed 'box
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Robertb
Long Beach


Joined: 01 Sep 2003
Posts: 6769
Location: South Oxfordshire

2002 Porsche 996 Carrera 4S

PostPosted: Wed Jan 30, 2019 4:04 pm    Post subject: Reply with quote

Had a very similar experience with my 3.6 on millers 10/50. Not using anything else now!

I will be interested to see how its oil usage compares, not that it used very much.
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MisterCorn
Long Beach


Joined: 08 Jan 2011
Posts: 6596
Location: Nottingham, England

2004 Porsche 996 Turbo

PostPosted: Wed Jan 30, 2019 4:26 pm    Post subject: Reply with quote

You put a higher viscosity oil in and you now get higher pressure at idle when warm. Isn't this exactly what you would expect irrespective of the brand of oil used?

MC
 
  
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asterix_the_gaul
Suzuka


Joined: 20 Dec 2008
Posts: 1193
Location: Cheshire

1999 Porsche 996 Carrera 2

PostPosted: Wed Jan 30, 2019 6:39 pm    Post subject: Reply with quote

You also increase pressure by chucking in some more oil, Max oil or a tiny bit more gives you healthier pressures than running oil in middle of the range or below.
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1995 993 C2 Cabriolet, Midnight Blue/Marble grey -gone!
1999 996 C2 Coupe, Ocean Blue/Graphite grey
2002 E46 M3 Cabriolet, Laguna seca blue/LSB
 
  
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alex yates
Le Mans
Le Mans


Joined: 06 Mar 2014
Posts: 15227
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Wed Jan 30, 2019 6:45 pm    Post subject: Reply with quote

MisterCorn wrote:
You put a higher viscosity oil in and you now get higher pressure at idle when warm. Isn't this exactly what you would expect irrespective of the brand of oil used?

MC


Beat me to it. Thicker oil = higher pressure.
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diverzeusy
Österreich


Joined: 10 Nov 2012
Posts: 954
Location: Doncaster UK


PostPosted: Wed Jan 30, 2019 7:18 pm    Post subject: Reply with quote

yep, thicker oil = higher pressure,
and also my logic thinking out loud, if a car has 70/80/90k miles or more on it, then surely a thicker than standard oil is a good thing to take up any minor and normal wear tolerances, or put another way the thin oil is really now too thin for an older engine.?? Dont know
what do you think Thumb
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alex yates
Le Mans
Le Mans


Joined: 06 Mar 2014
Posts: 15227
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Wed Jan 30, 2019 7:22 pm    Post subject: Reply with quote

Oh no, don't start that.
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MisterCorn
Long Beach


Joined: 08 Jan 2011
Posts: 6596
Location: Nottingham, England

2004 Porsche 996 Turbo

PostPosted: Wed Jan 30, 2019 7:22 pm    Post subject: Reply with quote

asterix_the_gaul wrote:
You also increase pressure by chucking in some more oil, Max oil or a tiny bit more gives you healthier pressures than running oil in middle of the range or below.


It shouldn't do. Unless the extra volume makes it slightly cooler/thicker.

MC
 
  
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kas750
Reims


Joined: 31 Mar 2013
Posts: 4279
Location: Chorley lancashire

2006 Porsche 911

PostPosted: Wed Jan 30, 2019 7:43 pm    Post subject: Reply with quote

MisterCorn wrote:
asterix_the_gaul wrote:
You also increase pressure by chucking in some more oil, Max oil or a tiny bit more gives you healthier pressures than running oil in middle of the range or below.


It shouldn't do. Unless the extra volume makes it slightly cooler/thicker.

MC


Indeed.I would be interested in the theory behind that.
 
  
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diverzeusy
Österreich


Joined: 10 Nov 2012
Posts: 954
Location: Doncaster UK


PostPosted: Wed Jan 30, 2019 8:16 pm    Post subject: Reply with quote

alex yates wrote:
Oh no, don't start that.

Floor Floor Hand Hand Floor Floor
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asterix_the_gaul
Suzuka


Joined: 20 Dec 2008
Posts: 1193
Location: Cheshire

1999 Porsche 996 Carrera 2

PostPosted: Thu Jan 31, 2019 7:10 am    Post subject: Reply with quote

kas750 wrote:
MisterCorn wrote:
asterix_the_gaul wrote:
You also increase pressure by chucking in some more oil, Max oil or a tiny bit more gives you healthier pressures than running oil in middle of the range or below.


It shouldn't do. Unless the extra volume makes it slightly cooler/thicker.

MC


Indeed.I would be interested in the theory behind that.


No theory at all, just observation. Dash meter read in the middle, low idle pressure kissing 1bar, topped up oil, overcooked it and dash reads 1 digit over Max and got 1.5bar idle. After last service repeated and got same result.
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1995 993 C2 Cabriolet, Midnight Blue/Marble grey -gone!
1999 996 C2 Coupe, Ocean Blue/Graphite grey
2002 E46 M3 Cabriolet, Laguna seca blue/LSB
 
  
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ballcock
Sepang


Joined: 21 Jul 2008
Posts: 2943
Location: Dublin

1996 Porsche 993 Carrera 2

PostPosted: Thu Jan 31, 2019 7:58 am    Post subject: Reply with quote

I can’t think of any scientific law that would agree with the above, not saying it doesn’t happen, I just can’t figure WHY .. unless it’s down to how the pressure gauge or sender operates?
Anyway, my guage is as before, filled to just below max
With regards to higher pressure after the oil change it makes perfect sense to me .. higher hot visosity = higher idle oil pressure. And to be fair I believe I have gone from a W30 to a W50.

It also makes sense to me that the higher hot viscosity will protect higher mileage bearings ... Each to their own tho Razz
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‘98 Ocean blue 996 C2 Tip pressed into daily service.

Ex '83 W460 LWB G Wagen updated with OM602 engine and 6 speed 'box
Ex. '99 996 C2 manual coupe.
 
  
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MisterCorn
Long Beach


Joined: 08 Jan 2011
Posts: 6596
Location: Nottingham, England

2004 Porsche 996 Turbo

PostPosted: Thu Jan 31, 2019 8:11 am    Post subject: Reply with quote

ballcock wrote:
I can’t think of any scientific law that would agree with the above, not saying it doesn’t happen, I just can’t figure WHY .. unless it’s down to how the pressure gauge or sender operates?
Anyway, my guage is as before, filled to just below max
With regards to higher pressure after the oil change it makes perfect sense to me .. higher hot visosity = higher idle oil pressure. And to be fair I believe I have gone from a W30 to a W50.

It also makes sense to me that the higher hot viscosity will protect higher mileage bearings ... Each to their own tho Razz


I tend to agree. The implication from Robertb's post which followed yours was that it was somehow the fact that it was Millers oil which was used which caused the effect, both posts specifically mention the brand. In reality you would see the effect with any brand oil when changing to a thicker oil. I'm not saying that Millers is good or bad, just that it has precious little to do with the change in pressure.

MC
 
  
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steve1
Spa-Francorchamps


Joined: 08 Feb 2009
Posts: 329


2002 Porsche 996 Carrera 2

PostPosted: Thu Jan 31, 2019 11:18 am    Post subject: Reply with quote

By using thicker oil you are only increasing the reading on a gauge, the pressure increases in front of the bearings by reducing the flow across them, and reducing the oil throw up the bores.
you have to decide which is best, more flow with thinner oil or less flow with thicker oil.
Just got to wait for an expert now.
Grin
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Diggermeister
Nürburgring


Joined: 26 May 2015
Posts: 380



PostPosted: Thu Jan 31, 2019 2:08 pm    Post subject: Reply with quote

I'm confused. What tyres have we decided to run, what oil and how much of it are we putting in them, and what grade of unleaded are we pouring over them?
 
  
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alex yates
Le Mans
Le Mans


Joined: 06 Mar 2014
Posts: 15227
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Thu Jan 31, 2019 2:51 pm    Post subject: Reply with quote

Anything that gets it from A to B quicker Laughing
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ballcock
Sepang


Joined: 21 Jul 2008
Posts: 2943
Location: Dublin

1996 Porsche 993 Carrera 2

PostPosted: Thu Jan 31, 2019 3:43 pm    Post subject: Reply with quote

MisterCorn wrote:
ballcock wrote:
I can’t think of any scientific law that would agree with the above, not saying it doesn’t happen, I just can’t figure WHY .. unless it’s down to how the pressure gauge or sender operates?
Anyway, my guage is as before, filled to just below max
With regards to higher pressure after the oil change it makes perfect sense to me .. higher hot visosity = higher idle oil pressure. And to be fair I believe I have gone from a W30 to a W50.

It also makes sense to me that the higher hot viscosity will protect higher mileage bearings ... Each to their own tho Razz


I tend to agree. The implication from Robertb's post which followed yours was that it was somehow the fact that it was Millers oil which was used which caused the effect, both posts specifically mention the brand. In reality you would see the effect with any brand oil when changing to a thicker oil. I'm not saying that Millers is good or bad, just that it has precious little to do with the change in pressure.

MC


Ah right MC! I get your point now. Absolutely NOTHING todo with the brand of oil I put in , that was just a bit of extra (useless) info.
ANY W50 oil would have achieved the same results.
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'96 Iris C2 vario manual coupe, Koni FZD's/M033's RSR's and HID's.
‘98 Ocean blue 996 C2 Tip pressed into daily service.

Ex '83 W460 LWB G Wagen updated with OM602 engine and 6 speed 'box
Ex. '99 996 C2 manual coupe.
 
  
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ballcock
Sepang


Joined: 21 Jul 2008
Posts: 2943
Location: Dublin

1996 Porsche 993 Carrera 2

PostPosted: Thu Jan 31, 2019 3:47 pm    Post subject: Reply with quote

steve1 wrote:
By using thicker oil you are only increasing the reading on a gauge, the pressure increases in front of the bearings by reducing the flow across them, and reducing the oil throw up the bores.
you have to decide which is best, more flow with thinner oil or less flow with thicker oil.
Just got to wait for an expert now.
Grin


Yes, good point to an extent, but when you reach the stage where you’re liable to have less than one bar (on the one hot summers day we get in Dublin , stuck in traffic etc) then I would have felt that oil with a thicker HOT viscosity makes good sense.
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'96 Iris C2 vario manual coupe, Koni FZD's/M033's RSR's and HID's.
‘98 Ocean blue 996 C2 Tip pressed into daily service.

Ex '83 W460 LWB G Wagen updated with OM602 engine and 6 speed 'box
Ex. '99 996 C2 manual coupe.
 
  
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skinny_monkey
Nürburgring


Joined: 16 Sep 2014
Posts: 400



PostPosted: Thu Jan 31, 2019 9:32 pm    Post subject: Reply with quote

ballcock wrote:
I can’t think of any scientific law that would agree with the above, not saying it doesn’t happen, I just can’t figure WHY .. unless it’s down to how the pressure gauge or sender operates?
Anyway, my guage is as before, filled to just below max
With regards to higher pressure after the oil change it makes perfect sense to me .. higher hot visosity = higher idle oil pressure. And to be fair I believe I have gone from a W30 to a W50.

It also makes sense to me that the higher hot viscosity will protect higher mileage bearings ... Each to their own tho Razz


You're reading the oil viscosity wrong. The W beings to the first number. Like 0W or 5W

As for higher viscosity causing less flow, the pump sets the flow rate. The higher viscosity just means it has to work harder. But the higher viscosity is what keeps your bearing surfaces apart
 
  
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