Idle oil pressure?

[GranburyChuck]

Got a 2000 C2 996. Recently noticed that the oil pressure at idle is about 1 maybe a little less. Is this an issue? I don't seem to be loosing oil. Typically it stays the same place on the dipstick until I change it at about 10k miles. Thought I might have an AOS issue but I don't have any smoke on start-up. I have read others having about 1.5 bars at idle (when engine warm).

Comments?

[1999Porsche911]

When you change oil, don't replace it with Mobil 0W40. Put a better and higher vicosity oil in the engine. You never want to see less than 1.5 bar at idle. I suggest a 5W50 or 15W50 on the 3.4 engine.

[wvicary]

Nothing wrong with 1 bar at idle. 0w40 is Porsche recommended weight.

[GranburyChuck]

I have been using Mobil 1 0W40 but recently went 10W40 as it was in the manual. Just changed about 7000 miles ago. Should I go back to 0W40?

[1999Porsche911]

Nothing wrong with 1 bar at idle. 0w40 is Porsche recommended weight.

That would be true IF your gauge reading of 1 bar was accurate. However, it is not even close. :D

[scottiemac]

Got a 2000 C2 996. Recently noticed that the oil pressure at idle is about 1 maybe a little less. Is this an issue? I don't seem to be loosing oil. Typically it stays the same place on the dipstick until I change it at about 10k miles. Thought I might have an AOS issue but I don't have any smoke on start-up. I have read others having about 1.5 bars at idle (when engine warm).

Comments?

I have a 99 C2 Cab and have been running Mobil 1 5W50 for about a year. I tried it because some of the other grades weren't available. At idle when engine is up to temp I get 1.5 bar. Car starts easily when cold (I live in the Great White North).

[wvicary]

Nothing wrong with 1 bar at idle. 0w40 is Porsche recommended weight.

That would be true IF your gauge reading of 1 bar was accurate. However, it is not even close. :D

And what makes you think it's not accurate?? The specs I found for this engine are 5 bar@5000 RPM with a oil temp of 90C. I think you might be trying to fix something that isn't broken.

[1999Porsche911]

Nothing wrong with 1 bar at idle. 0w40 is Porsche recommended weight.

That would be true IF your gauge reading of 1 bar was accurate. However, it is not even close. :D

And what makes you think it's not accurate?? The specs I found for this engine are 5 bar@5000 RPM with a oil temp of 90C. I think you might be trying to fix something that isn't broken.

All you have to do is replace your electronic sensor with a mechanical pressure gauge to see the real reading. Mobil Water is not vicious enough to properly protect bearings during low pressure and high load conditions. Just like your coolant gauge, your pressure gauge is no more than an idiot light as far as accuracy goes.

[phillipj]

What oil do you suggest other than "Mobil Water"? :D

What brand do use in your car and what weight?

Thanks!

[AKellog]

Nothing wrong with 1 bar at idle. 0w40 is Porsche recommended weight.

That would be true IF your gauge reading of 1 bar was accurate. However, it is not even close. :D

And what makes you think it's not accurate?? The specs I found for this engine are 5 bar@5000 RPM with a oil temp of 90C. I think you might be trying to fix something that isn't broken.

All you have to do is replace your electronic sensor with a mechanical pressure gauge to see the real reading. Mobil Water is not vicious enough to properly protect bearings during low pressure and high load conditions. Just like your coolant gauge, your pressure gauge is no more than an idiot light as far as accuracy goes.

That is incorrect advice regarding the viscosity of Mobile 1. I am a Chemical and mechanical Engineer and can tell you the viscosity is just fine for protecting the bearings at low and High Pressures. The only instance where it would not be able to protect would be in extreme heat conditions that would be from running your Porsche at very high speeds 150 MPH Plus for a long period of time (45-minutes to an hour). As far as the accuracy of the Temp guarge, that is also incorrect. While a Porsche Thermister, which reads the temperature, is not as accuarate as an F1 Glosken Gauge, it is accurate enough to Plus or minus 1.9 degrees in the normal running spectrum. The other consideration is the effect of altitude and possible humidity in the thermistor, but the negative impact on the thermistors readings are negligable.

Edited April 9, 2009 by AKellog

[Loren]

Porsche's current "Approved Engine Oils" list includes only 0W-40, 5W-40, and 5W-50.

The complete TSB is available here to all Contributing Members.

[wross996TT]

FWIW 1999 has been bad mouthing 0W40 forever...I have read multiple reports from competent people (such as Doug Hillary who did an extensive test on oils). Remember oil is not just for lubrication, but also for cooling. I am fine sticking with Porsche recommended oils: 0W40, 5W40, 5W50 for normal use. BTW, the most critical lubrication time is a start-up. The thicker the weight the less lubrication (first number on the multi-weight oils) at start.

[phillipj]

Great info

Thanks

[1999Porsche911]

FWIW 1999 has been bad mouthing 0W40 forever...I have read multiple reports from competent people (such as Doug Hillary who did an extensive test on oils). Remember oil is not just for lubrication, but also for cooling. I am fine sticking with Porsche recommended oils: 0W40, 5W40, 5W50 for normal use. BTW, the most critical lubrication time is a start-up. The thicker the weight the less lubrication (first number on the multi-weight oils) at start.

Old wive's tail. The fact is, 15W50 and 0W40 oil flow to ALL engine componants at EXACTLY the same speed using the stock oil pump. Therefore, flow is of absolutetly no concern. However, 15W50 will remain on the upper parts of the engine longer than will Mobil Water, therefore protecting the engine better.

You need to seperate the marketing "facts" from the performance facts. Viscocity is a measurement of flow by gravity and not under pressure or vacuum. Higher oil pressure does not mean less flow, but it does mean that parts are seperated better.

The flow facts can easily be tested on your engine while in your car. It has been done many times.

Edited April 9, 2009 by 1999Porsche911

[perryinva]

Is there a Mobil 1 5w-40 or 5W-50? That would seem ideal if you want a higher cold pressure. However, both 0W-40 and 5W-40 would both yield about the same hot oil idle pressure. The 0W and 5W only come into play when the oil is cold. Also, keep in mind that the pressure indicated is the pressure at the sender, not in the oil channels. It stands to reason that the lower the overall viscosity, the higher the flow, which is just as important as pressure. However, f there is any blockage,due to dirt, metal shavings etc, I would think that the higher pressure would have a better chance of flushing it out over flow, so it may be a 6 of one, 1/2 dozen of the other situation. a 5W-50, as 1999 advocates would give you a higher pressure as hot idle.

I am also a mechanical engineer of 30 years, and while I have taken tribology courses, I have to admit that I'm not sure where 1999 gets the "old wives tale" that lower viscosity flows the exact same as higher viscosity. That would only be true for a positive displacement pump, which all automotive oil pumps that I have ever seen, including the 996s certainly are not. They are gear driven or impeller driver pumps. I deal with pumps and different oils for burning and lubrication all the time, and I have never come across that. But like I said, I'm not an engine lubrication expert, just educated enough to be dangerous. Viscosity and lubrosity (shear protection) are not related. Every bearing/journal, etc has at least 2 wear planes, inner and outer. The correct viscosity simply allows adequate flow to the (supposedly engineered correctly) location distribution point that distributes the oil in a way that allows a balanced shear to occur in both wear planes, and that correctly counters the mechanical force of the engine part. The oil shears and carries away heat in a balanced synergy. Too low a viscosity, and the part to part contact may occur in one of the planes. Too high a viscosity and inadequate oil is supplied that may allow contact in either one or both planes and overheating. Consensus agrees that mostengine wear occurs at startup, but loss of oil destruction occurs at highest stress due to lack of lubrication/cooling at the subject bearing. I believe it is splitting hairs in non winter use to choose 0W-40 over 5W-40 or visa versa. Certainly, the lowest viscosity available will flow faster to cold parts, and have less parasitic loss to increase MPG and performance. Once up to temp, they have to behave the same.

Edited April 9, 2009 by perryinva

[1999Porsche911]

Is there a Mobil 1 5w-40? That would seem ideal if you want a higher cold pressure. However, both 0W-40 and 5W-40 would both yield about the same hot oil idle pressure. The 0W and 5W only come into play when the oil is cold. Also, keep in mind that the pressure indicated is the pressure at the sender, not in the oil channels. It stands to reason that the lower the overall viscosity, the higher the flow, which is just as important as pressure. However, f there is any blockage,due to dirt, metal shavings etc, I would think that the higher pressure would have a better chance of flushing it out over flow, so it may be a 6 of one, 1/2 dozen of the other situation. a 5W-50, as 1999 advocates would give you a higher pressure as hot idle, but I do not know if that is on the approved Porsche list.

0W40 and 5W40 WILL NOT deliver that same oil pressure, hot or cold. Even 2 different 0W40 oils will most likey not deliver the same pressure. The range allowed to call an oil 40 weight is HUGE.

[GranburyChuck]

Since a 5W-50 is a Porsche approved oil I will try that soon and let everyone know.

I am a chemist, polymer chemist, materials scientist, biochemist, biophysicist and proud Porsche owner. FWIW. Perry, you were going to give me the part numbers for the additional components I need to use on the PSS9s.

[wross996TT]

Old wive's tail. The fact is, 15W50 and 0W40 oil flow to ALL engine componants at EXACTLY the same speed using the stock oil pump. Therefore, flow is of absolutetly no concern. However, 15W50 will remain on the upper parts of the engine longer than will Mobil Water, therefore protecting the engine better.

You need to seperate the marketing "facts" from the performance facts. Viscocity is a measurement of flow by gravity and not under pressure or vacuum. Higher oil pressure does not mean less flow, but it does mean that parts are seperated better.

The flow facts can easily be tested on your engine while in your car. It has been done many times.

Could you define fact please?...seems to me you have opinions (perhaps hypotheses) but NO DATA to support your claims.

read post 66

Search on Doug Hillary and you will find someone who has studied oil in Porsches and actually has data instead of being an internet jockey.

[1999Porsche911]

Old wive's tail. The fact is, 15W50 and 0W40 oil flow to ALL engine componants at EXACTLY the same speed using the stock oil pump. Therefore, flow is of absolutetly no concern. However, 15W50 will remain on the upper parts of the engine longer than will Mobil Water, therefore protecting the engine better.

You need to seperate the marketing "facts" from the performance facts. Viscocity is a measurement of flow by gravity and not under pressure or vacuum. Higher oil pressure does not mean less flow, but it does mean that parts are seperated better.

The flow facts can easily be tested on your engine while in your car. It has been done many times.

Could you define fact please?...seems to me you have opinions (perhaps hypotheses) but NO DATA to support your claims.

read post 66

Search on Doug Hillary and you will find someone who has studied oil in Porsches and actually has data instead of being an internet jockey.

I do not state as "fact" things I read or hear about. That would have to be classified as hearsay. Personal experience and testing is what makes it a fact. I might also ask you to provide ANY data of ANY testing that has been done EVER to prove that the oil flow in the engine is inhibited when moving from a 0W40 to a 15W50. Seems to me that people prefer to accept a conscientious as fact with no proof, yet want all kind of proof from those who know differently.

The argument made by Doug in the link you supplied begins with an incorrect assumption: That the viscosity of an oil affects its flow the same under gravity as it does under pressure. Therefore, garbage in, garbage out. Viscosity IS NOT a measurement of the flow of an oil in an engine.

[carsareart]

I am using 5w50 syntec. One thing I noticed when I changed from 15w50 mobil 1 was the lack of valve noise on start up now. I allow my engine to idle for 30 sec to 1 min before I move the car out of my garage. When I was using 15w50 there was more noise from the engine during the first few seconds of runtime. I would like to find 5w50 mobil 1 but can not in my area.

I do autocross about once a month.

1999, 120,000 miles.

[wross996TT]

I do not state as "fact" things I read or hear about. That would have to be classified as hearsay. Personal experience and testing is what makes it a fact.

Sorry you are so wrong here...and you always call others out to show data (which I did and Doug Hillary has done) and yet you have NEVER SHOWN any data...Show data or stop preaching....I am out

[Loren]

I think pretty much everything has been said here - this thread is now closed.