mark kibort

91 race hours, 6 full seasons of 6500rpm shifting, high g turning racing, no coolers, accusump, etc and nothing found in the oil analysis or visibly in the filter over the 6 years ive owned this 20 year old car!
Amzoil 20-50 racing. If you dont believe in luck, its a pretty noteworthy record of performance, quite possibly impart due to the oil.
I was racing this weekend, AGAIN, and flogging the XXX out of the engine in 95 degree heat, 130 degree track temps, and oil pressure was stuck at 5 bar, even down the carocel as well as oil temps reaching near 275F.
Sure, with most all street cars, any oil will probably do fine, but if you track it, wouldnt you want to use one that showed some charateristics that may protect your engine in extreme use situations?

IMHO

mk

Bill Ball

The spec is 5 bars at 4000-5000 RPM (I've seen both RPMs in Porsche douments). However, 4 bars at 2000 sounds good....as long as it reaches 5 bars at 4-5000 RPM. However, I have seen a 91 where the meter pegs at 4.5 - a mechanical problem, not a pressure problem.

Aatos

Idle rambling..I've been checking out Castrol TWS 10W60 and Valvoline VR1 Racing 10W60. The TWS is ACEA A3 rated (hths>3.5) but I can't seem to find the ratings for the VR1 even though the VR1 10W60 is a semisynth.

worf928

Roger, I just copied this from the Mobil website:

If you can find good'ole M1 (and not the "extended performance" version) then I'm thinking we can stick with 15-50. Correction, see below

worf928

More digging on Mob's website:

I'm not going to toss the 4 gallons of 15-50 EP I have on a shelf.

Bill Ball

Doug has criticized the zinc - phosporous reduction alarmists.

heinrich

I use Mobil One 15W50 and I'm happy with it. My oil pressure gauge shows 3 or sometimes a hair less at idle and sometimes a hair more, and 5 at any revs. When starting, it goes immediately to 3 and jumps to 5 in a second. This happens on ALL my 928's. Same. Same pressures, same conditions.

worf928

1) Doug sold his 928 (gotta wonder about that, casts his reports in a new light...)
2) He doesn't have two sets of GT cams that like to pit.
3) You run 15-50 right

All humor aside, oils in the 70s, 80s, and 90s had ZDDP in it. That's what our motors were design to run with, tested with, and shipped with. I don't really care if the factory says that, now, we can run 0-40 with our Boxster ... opps... they meant 928 engines ... when the owner's manual says 20-50 works. They barely trickle parts to us (still waiting for a lower oil cooler hose for an '87 after three months), so I doubt they actually gave the 928 a minutes thought when they posted their 'new' recommended oils. I'm pretty sure that Dr. W would like to have all 928s off the road.

All hysterics aside, as long as I can easily find 15-50 that I know has some ZDDP in it I'll use it preferentially. I will give the M1 0-40, that Doug lavishes praise on, a try in either the GTS or the '91. For the '89, I'm going to Castrol 20-50 Dyno Juice (I've two cases that are 10+ years old so I *know* that there's tons of ZDDP in it ) to see if the thick stuff will cure the clacking lifters until I get the energy to pull its heads and cure it for real. The '89 really didn't like Castrol 5w-50 SuperSynth so that's out.

As far as I can tell, and I recall Doug confirming, M1 15-50 meets or exceeds all the specs even if it isn't on the PAG approved list. Maybe I'm wrong.

ELJG

Thanks Bill,

I was concerned that the pressure might be too high, too soon. By 4000 rpms it's definitely at 5 bar. Car has over 112k on the clock, is not tracked and UK temps tend not to be extreme... so Amsoil 20 50 or Mobil 15 50?

unit

[QUOTE=worf928;4540076]1) Doug sold his 928 (gotta wonder about that, casts his reports in a new light...)


I have dougs old car. i didnt buy it from him but from the Porsche dealer he traded it in on.
I can tell you the car is in very good order and when i purchased it running on
delvac 5w 40 THIS car held very good oil pressure.
Im not saying that this oil is or isnt good. i think it depends on when, how, where you drive the car.
I wouldnt like to drive a car with the oil light on as stated in previous posts.

Im going to follow my own judgment.

Sam

Alan

Mike - based on everything i have seen - if your car never goes below 3bar even at hot idle - you may have a problem with your gauge/sender/pressure valve unless you are always running some heavy oil.... (Unless your definition of hot is different than mine - 100F+ days)

Just seems best case is 2.5bar at hot idle and that is quite normal. I'd be happy with 2 bar or actually even 1.5bar worst case...

I do not think the low oil pressure warnings are due to faulty equipment - there are just too many reports from folks with well maintained newer cars - who have checked out or changed out all the usual suspects.

I think it may well be the nature of the oil pressure monitoring method... maybe low measured oil pressure is actually OK for lubrication with some oils in some instances - I think thats what Doug was saying...

However how acceptable is that... are we supposed to just ignore low oil pressure warnings...

Alan

Herman K

FYI,

I’ve read Doug’s post a few months ago and based on it I’ve changed to Mobil 1 5W-40.
I get full scale oil pressure when the engine is cold. When hot (185-190) and at idle (685 RPM) the gauge is at 1.8-2.0. Whenever the RPM is at 4000 and over the gauge is at a minimum of 4.5-5 I’ll blow out approximately a quart of oil per 700 -1000 miles depending on how hard I’m driving (read: depending on how many times I get challenged in the “Red Rocket”, done some dusting work lately with the miracle cure of two fuel pumps working). With the replenishing of the oil and the Mobil 1 5W-40 the appearance on the dip stick is always pretty clean and it appears to me that I’ve less oils seeping from gaskets that still need to be replaced (MM & Pan, haven’t been able to schedule time for time jet).

1994 GTS 5spd

Mike Frye

Alan,

Thanks for the response. This is my first 928, and I only have it and what I read on here as a guide. As Bill said, there doesn't seem to be anything in the manual about a 'normal' reading, just that it should display 5 bar at high revs and what it means if the light comes on.

I agree that there hasn't been a direct relationship established between displayed oil pressure and actual lubrication capabilities/protection. Some will assert that showing 5 bar on the gauge when hot is an indication of healthy lubrication (MK) and I tend to believe that higher pressure is better than lower pressure, in general. I just wanted to put it out there that my assumption in the absence of any documentation to the contrary was that the gauge was set up to display mid-way (3 bar) when running normally (warmed up, at idle) and maxing out under the most extreme conditions of high RPMs (5 bar).

I'm not sure if this idea came from the fact that my car displays these characteristics or the fact that most of the gauges I've seen in the cars/boats I've owned and driven have been set up this way.

If the general consensus is that a warm car at idle should display as low as 1.5 bar, as long as it goes up to 5 bar at 4k+, then I guess I need to look at mine more closely and find out if I'm making my car work harder than it has to by using the wrong viscosity or if there's an electrical or mechanical problem that can be fixed.

I'm not sure this is the case though, since Heinrich confirmed that his cars all run just over or just under 3 bar at idle.

Maybe I'll take a poll just to see if I can determine for each model year what's 'normal' based on experience, not design and then everyone can learn a little from that.


Ernest,

Sorry if my response caused this whole hijack/derailment of your post. I honestly wasn't trying to stir up a hornet's nest, I just thought either your car or mine is showing a problem with the gauge. I assumed it was yours, but maybe it's mine.

Alan

Heinrich lives in the great northern cold wastelands - he doesn't encounter such temperatures - he's lucky to see the sun for half the year.... (bit like New Jersey really). Maybe ambient temp is the major deal here...

However don't get me wrong - I think 3 bar is great - but you never really know if the gauge is telling you the truth - same with all the dash gauges really...

Some will have higher pressures because of lower ambients and generally heavier oil - e.g. Kibort runs 20W50 I think and says he gets good pressures consistently.

Alan

Aatos

Okay, so what's needed to get accurate pressure readout?