ErnestSw

Some time ago I posted a thread about my oil pressure light coming on at idle and my pressure gauge reading below 1 bar at idle. A big discussion ensued with me insisting it wasn't the oil, but with some people noting that when they changed to Delvac 5w40 their oil pressure dropped and their lights came on as well. I then assumed that it must be a change in the formulation of Delvac 5w40 and determined to change my oil. I haven't gotten around to it yet.
Today Pam and I went on a lovely trip to Vermont. Ambient temp around 80F (same as when I posted about the drop in pressure) and the oil pressure stayed at 1.5 bar at idle and no lights came on.
(PLAY THEME FROM TWILIGHT ZONE)

John Struthers

A happy couple, a dream get-away car, and a beautiful day.
Cruising the back roads of Vermont (ain't they all?) without a worry in the world...till...
they spot a road sign. Just ahead. And make a fateful turn into the TW Zone.
Maybe that Delvac has to be beaten a bit then let to rise Ern. You know, like bisquit dough.
Then it thickens and...coming Mr Serling.

IcemanG17

Ernest
5-40 is light for a 928 that was designed for 20-50.....& make sure to change the springs in the oil thermostat too...my got weak and would cause low oil pressure at idle after it was very hot then shut off and restarted (think after getting gas)

Jack Riffle

Or theres enough metals suspended in the oil to thicken it so as to increase the pressure..... Sorry......couldn't resist.

John Struthers

stop it Jack, yer killin' me.
And you might worry Ern a bit.
Ern could put a heavy duty rod type 'earth magnet at the botton of the oil pan.
Or, ......
Joking Ern,

ErnestSw

Jack,
I sure hope yer not a doctor------Got a sore throat Mrs Jones? Hmmmm, could be cancer.
John,
Where the hell you been? I wuz worried you'd choked on the hydrocarbon fumes.

ColinB

Ernest
When I had my car in for it's 120 000km service I specified a 20-50 oil. (Shell Helix) and the shop assured me that's what they used. But they didn't. The result was a hot idle pressure of 1.5 bars and CHECK OIL warning light. Max at 4000 rpm was 4+. Since this was my regular 'trusted' workshop I was a bit confused until I changed the oil again as a precaution 1000km later. Voila! 2+ bars at hot idle, no warning light and nearly 5 bars at 4000 rpm.

Won't trust them again. I'll change it myself in future. Go to a good quality 20-50 and sleep easy.

Colin. 89GT.

Mike Frye

Ernest,

I still don't think 1.5 bar is enough. In my car, even when it's fully warmed up, it never dips below 3 bar. If it does, I'm a little low on oil.

I forget what the rate is, but these cars were designed to consume some oil over time. If you're middle of the dipstick or higher, I think you should be at 3 bar at idle, going up to 5 bar if you're over 4k or so.

IMHO, you've still got a viscosity/brand of oil issue.

Just my .02

Peter F

Related discussion ongoing at the UK 928 forum made one of them contact Porsche in Germany.
They came back with a list of the most current recommendations.

http://www.928.org.uk//content/view/104/119/

/Peter

ROG100

This info from Porsche is allways confusing to me and seems like a "lets cover all bases" sheet of info.
These are lists of approved oils as opposed to oils you can use in your specific car at whatever ambient temp. your car is running in.
The only temperature consideration is below -25C and above -25C. Wht about those of us at the other end of the temp. spectrum that run in ambients of +40C.
If I look at my manual it clearly states that I must use 20W 40 or 20W 50 in Texas.
I recently changed to 5W 40 and lost a serious level of oil pressure.
If I use 0W 40 in my car and it is an approved oil will Porsche cover me for any damge to my engine????????
The bigger the difference between the low number and the high number means more additives/enhancers

ckabee1

I have been following these oil viscosity discussions with interest, as my first oil change is coming due soon. My owner's manual indicates a 5w-40 synth is appropriate for my area and the above porsche approved link aslo indicates mostly 0w and 5w-40 oils.

Delvac 5w-40 seems to have been beaten to death and oddly enough, it is not on the list (unless it falls under one of the Mobil 1 categories). Either way, it does not seem to work for many folks.

PO used Mobil 1 according to receipts, but I'm unsure of the viscosity. My gauage pegs at WOT, and sits at 2bar at idle. It did dip to 1.5 on the 100+ days, but no OP warning.

My thoughts are to use the recommended 5w-40, which seems appropriate for Upstate South Carolina, and take a print-out of the approved list and see what Wal-Mart carries.

Until Rotella T or Delvac makes the "list", they are not going in my car.

...My $.928 worth...

ErnestSw

The assumption seems to be the more pressure the better. Think about pressure as a force to overcome resistance. If the oil flows more easily into the smaller openings there will be less (back) pressure and better flow.
Viscosity is NOT the same as lubrication ability.

ckabee1

Fluid dynamics and motor oil characteristics are beyond my abilites to comprehend. My area of expertise is in psychology and psychometrics, so please forgive me.

I can't help but think that if one sticks to the recommendations by the professionals (Porsche engineers) and still experience an oil pressure warning, there is a bigger issue than the oil?

I am not trying to get flammed or start a war, I'm just confused and want to take the easy way out while still protecting my baby.

How do you change the springs in the oil thermostat? I have not seen that before.

Mike Frye

Ernest,

Not trying to find trouble where none exists.

Your point is well made and I'm certainly not disagreeing with it, I'm just saying that I think the car was designed to run in the middle of the gauge, which is 3 bar. If it's below that I think it's out of its normal operating parameters. This may be a gauge or voltage problem, or it may be a real pressure problem, but IMHO, it's a problem.

YMMV

ROG100

As I, and I alone, have to make the decision on what oil to put in my GTS I am going with Royal Purple
20W 50 as per the recommendation in my manual and after considering all the info in this and many other threads. Delvac was an ideal choice because of the retention of Zinc (wear protection) which has been removed from many of the other commercially available oils. However its lower viscosity at the cold end of the spectrum and the large amount of enhancers (less lubrication) which has given a few of us problems with OP has removed it from my car. This is a major factor in my choice of Royal Purple. We will see what we will see8>)
I will also live with the consiquences.