Is this oil pressure ok?
10-29-2004, 11:55 PM
#17
Burning Brakes
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Hi,
during the last 10 years retrospective Bulletins from Porsche have suggested the use of a Group 3 synthetic oil as a minimum.
This, along with the need for a lubricant with a minimum HTHS viscosity of 3.5cSt, means that their 5w-40 recommendation for use all year round is an excellent one. This applies to temperatures from below -20F to above 100F. A 5w-50 can also be used but there are some benefits in using the 5w-40 viscosity - this is mainly to do with the valve train and oil filter bypass and especially the hydraulic adjusters. A suitable oil should have the ACEA ratings of both A3 and B3 on its container
Idling oil pressure is not a published Porsche specification and as long as the low oil pressure light is not triggered and you have 4 to 5bar at 4000rpm with the oil at 80C, all is well
Some oils (especially synthetics) will show less pressure at idle than others - Mobil 1 is such an oil. This is due to their superior flow charactertics and of course oil flow is maintained because the oil pump has a constant displacement according to engine speed
A 10w-30 oil is not a good choice in Porsche engines as it does not meet Porsche's minimum HTHS viscosity. This viscosity oil will tend to show up to one bar lower oil pressure when hot. A 5w-40 oil is the correct choice! If the engine is worn and using oil a 5w-50 oil may be used with confidence
The lower number (?w)-?? not the higher number ?w-(??) dictates how the oil will behave when cold!
Regards
Doug
during the last 10 years retrospective Bulletins from Porsche have suggested the use of a Group 3 synthetic oil as a minimum.
This, along with the need for a lubricant with a minimum HTHS viscosity of 3.5cSt, means that their 5w-40 recommendation for use all year round is an excellent one. This applies to temperatures from below -20F to above 100F. A 5w-50 can also be used but there are some benefits in using the 5w-40 viscosity - this is mainly to do with the valve train and oil filter bypass and especially the hydraulic adjusters. A suitable oil should have the ACEA ratings of both A3 and B3 on its container
Idling oil pressure is not a published Porsche specification and as long as the low oil pressure light is not triggered and you have 4 to 5bar at 4000rpm with the oil at 80C, all is well
Some oils (especially synthetics) will show less pressure at idle than others - Mobil 1 is such an oil. This is due to their superior flow charactertics and of course oil flow is maintained because the oil pump has a constant displacement according to engine speed
A 10w-30 oil is not a good choice in Porsche engines as it does not meet Porsche's minimum HTHS viscosity. This viscosity oil will tend to show up to one bar lower oil pressure when hot. A 5w-40 oil is the correct choice! If the engine is worn and using oil a 5w-50 oil may be used with confidence
The lower number (?w)-?? not the higher number ?w-(??) dictates how the oil will behave when cold!
Regards
Doug
10-30-2004, 05:37 PM
#18
Hi,
One more data point on this.
I was running Mobil 1 15 - 50 in my 1994 968. Generally the guage read 2.5 at idle. and 5 while underway.
I just changed the oil to Mobil 1 0-40 and now at idle the guage reads 2.0 and 4.5 - 5 under way.
Phil
One more data point on this.
I was running Mobil 1 15 - 50 in my 1994 968. Generally the guage read 2.5 at idle. and 5 while underway.
I just changed the oil to Mobil 1 0-40 and now at idle the guage reads 2.0 and 4.5 - 5 under way.
Phil
Last edited by phil0618; 10-31-2004 at 09:56 AM.
10-30-2004, 06:08 PM
#19
Burning Brakes
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Hi Phil,
you said; "I was running Mobil 1 15 - 50 in my 1994 968'
What oil are you using now? Your oil pressure appears to be within the required range!
The relationship of flow to pressure is often misunderstood. Oil pressure is simply the resistance to flow. Flow is the product of the pump's displacement
The much superior flow characteristics of some synthetic lubricants can be misinterpreted as it tends to show a somewhat lower pressure. This is one reason why Porsche measures the oil pressure at specific engine revs (usually 4 or 5k), and the pressure must be 4 or 5bar - according to the engine family. The superior flow is an aid to heat management especially in turbocharged engines
In automotive terms 5bar is a very high operating oil pressure and is one reason why the correct oil quality rating and viscosity is so important
Regards
Doug
you said; "I was running Mobil 1 15 - 50 in my 1994 968'
What oil are you using now? Your oil pressure appears to be within the required range!
The relationship of flow to pressure is often misunderstood. Oil pressure is simply the resistance to flow. Flow is the product of the pump's displacement
The much superior flow characteristics of some synthetic lubricants can be misinterpreted as it tends to show a somewhat lower pressure. This is one reason why Porsche measures the oil pressure at specific engine revs (usually 4 or 5k), and the pressure must be 4 or 5bar - according to the engine family. The superior flow is an aid to heat management especially in turbocharged engines
In automotive terms 5bar is a very high operating oil pressure and is one reason why the correct oil quality rating and viscosity is so important
Regards
Doug
10-30-2004, 11:59 PM
#20
pcarfan944 - I'm afraid you have to worry about erratic oil pressure readings. As GlenL said, hopefullly it's electrical (sender, wires, maybe guage) but it might be real. Does the oil pressure indicator light built into the pressure gauge light up (I think it should for the ! light to come on)? That's a second signal from the sender than the one that drives the gauge.
You might check that your crank bolt is tight.
My story - I had an erratic oil pressure incident once (just once) and it went away. A week or two later, at the end of my morning commute, power steering went and oil pressure light and ! light came on as I was backing into my parking spot.. My crank bolt had fallen completely out (might have been loose for the first incident). Absolutely no damage (although towing and checking for damage was expensive). 2 minutes earlier I was at 75mph on I-95. So that can happen.
You might check that your crank bolt is tight.
My story - I had an erratic oil pressure incident once (just once) and it went away. A week or two later, at the end of my morning commute, power steering went and oil pressure light and ! light came on as I was backing into my parking spot.. My crank bolt had fallen completely out (might have been loose for the first incident). Absolutely no damage (although towing and checking for damage was expensive). 2 minutes earlier I was at 75mph on I-95. So that can happen.
10-31-2004, 03:06 AM
#22
Burning Brakes
Thread Starter
[QUOTE=gtroth]pcarfan944 - I'm afraid you have to worry about erratic oil pressure readings. As GlenL said, hopefullly it's electrical (sender, wires, maybe guage) but it might be real. Does the oil pressure indicator light built into the pressure gauge light up (I think it should for the ! light to come on)? That's a second signal from the sender than the one that drives the gauge.
You might check that your crank bolt is tight.
QUOTE]
Hi gtroth. The one time the lights did come on, it was so quick I didn't even notice what was on and what wasn't. Today has been much much cooler and I did a drive out to the Mall of America with no trouble at all, no trouble going to work today either. Thanks for the heads up on the crank bolt, where is that located for me to check? Thanks.
You might check that your crank bolt is tight.
QUOTE]
Hi gtroth. The one time the lights did come on, it was so quick I didn't even notice what was on and what wasn't. Today has been much much cooler and I did a drive out to the Mall of America with no trouble at all, no trouble going to work today either. Thanks for the heads up on the crank bolt, where is that located for me to check? Thanks.