Wolfman928

Eric, I believe many Porsche guys prefer w30 oils (because its for high performance, who worries about protection its a strong engine myth ) they want max performance out of their Porsche's and they are racer drivers, drive their cars hard and maybe from cold, who knows and that where most damage occurs over time.

have you heard this saying - "the car is suppose to handle it, it's a sports car, they are build to handle it..."

Like I said in the begining of the thread, I prefer 5 or 10w50, it provides a little more protection when hot or in hot climate areas and I would propably revert back to Fuchs oil or Mobil 1 if they stock 5/10w50

FredR

Hi Sean,

I do not know just how prevalent the problem is but I know it happens. If one sticks to the 20W50 with 1200 ZDDP I doubt there will be a problem. As a matter of interest did the owner have any history of what oil was in that engine?

When an owner has no clue what oil is in his car [as if often the case] then as you say it is a crapshoot plain and simple. One thing I did pick up on was that the ZDDP plating process works better the hotter the oil is [i.e. it does not work as intended with cold oil] so I am in good shape in that respect and may well get away with a lower spec of ZDDP. I know my cams are in perfect shape or were last time I checked a couple of years ago.

When I had my S4 motor rebuilt and plonked into the GTS chassis at the local agents 12 years ago I checked everything they did including the valve timing with the GTS inlet cams and the S4 exhaust cams combo Louie recommended for me. About the only thing I did not check was the oil! As I drove off on a nice hot June day with a big smile on my face things turned worrisome as the motor heated up and the idle pressure dropped to 1 barg- WTF? Drove back to the dealers somewhat gingerly and asked my mechanic what oil he put in the engine- Mobil 1 0W40! I just about blew a fuse and after calming down the maintenance manager [a good friend] told me that was what Porsche Middle East recommended for the car. I told them to drain it and stick it somewhere else, got some Shell Helix HX5 dino oil, mixed it with a pot of STP [plenty of ZDDP in it] and still do the same today. No problems to date touching the wood my head is made of.

What many do not seem to understand is that even main dealers now have problems dealing with 928s as more often than not they do not have folks left who know the car and what it needs. Thus why folks like yourself and your fellow professional colleagues who frequent this list are so precious as hopefully are DIY owners like myself who have kept their precious running for 20 years plus as we offer advice to newbies in the hope that it sinks in and helps them.

If they know better all well and good.

hacker-pschorr

I have no idea what you are going on about now, but even the 997 world doesn't drop down to 30wt oils:
https://rennlist.com/forums/997-foru...gine-oils.html

Side thought, if the widest spread multi-weight were the best option, why don't they just make a 0w-X in every weight? The answer is, it's not that simple. So again, just read the manual and follow it, best thing to do.

Years ago 5w-50 Castrol Syntec was the go-to oil for everyone, figured it must be the best since the 5 part would mean better cold starting lubrication! Nope, engines were lost (mine was one of them, 944S only street driven). Many Theorized the necessary modifiers to make such a wide spread meant it wasn't as stable, others say these engines were never made to run on such a thin film, even when cold (unless it's sub arctic conditions). The lower end specifications of the 944 is the same as the 928 FYI.

Wolfman928

I checked that charts, plenty of ZDDP in that Mobil 1 oils, all with w40 and higher has 1100 to 1300ppm and the race oils higher, there are some " High performance " versions which I'll stay away off...700-900ppm

Wolfman928

there are also guys here on the Forum that used 0w40 over the years with low level additives, the ones where they phased out Zinc and other metals to get away from damage on Cat converters, some of those guys claims 200k miles with their 928's without any problems....

hacker-pschorr

As my mother always said: "If all your friends jumped off a bridge, would you do it to?"

I guarantee you more people have reported issues with running thinner oil than recommended than those claiming they've gone over 200k documented miles.
AO & Myself were two of the most vocal. We tried two different high grades of 5w-40 based on the expert testimony from a respected Rennlister with a high knowledge of motor oil. Both of us experienced low oil pressure and lifter ticking at idle on warm days. Proof is in the pudding, why risk it? Your gauge could be a tad off and you may not hear the lifters.....

I'm not sure what your goal is here, what's next, arguing all the torque specs in the WSM are wrong? How about the recommended PSI for the tires is outdated since modern rubber is better? Why stop at just the motor oil? Are you putting Dextron VI in your transmission? It must be better since it's not "70's technology" - this one is extra tricky since the fluid back then was actually better, the contents were outlawed & lubrication companies have been trying ever since to match it.

It should be noted the primary reason anyone continues to post in threads like this is for the sake of others who may stumble in here.

But again....this all depends on climate. For a 928 that will never see ambient temps say above 70F, a proper 15w-40 could suffice. I'd be nervous running anything lower than 10-15 unless ambient temps are going to be below the rated temps for that weight, which again is below freezing. Which again, is all clearly listed in the WSM and owners manual. Easy to follow.

As for Castrol GTX, the last time I contacted Castrol was December 2017, thinking maybe you had some new information I replied back to their e-mail about GTX, ZDDP and older cars.
Here is their response which was just received:

Thank you for contacting Castrol North America.
Zinc data for Castrol GTX 20W-50 oil is not released however please note that Castrol GTX 20W-50 is not designed for older, flat tappet engines.
Castrol Consumer Relations

SeanR

Citations please.

Wolfman928

oh sorry, don't have a straight link or quote, just another question FredR / SeanR how could the oil pressure drop to 1 bar ? even with 0w30 it should not drop to 1 bar, clearly something else were off...my 928 at full temp use to sit in the middle(above 3 bar) and with the new 5w40 its just under 3 or touching 3 on a hot day (90 F++) at around 2000rpm as well, that's perfect IMHO...

the only noticeable difference I can see is that my car comes to temp faster with the 5w40 and it feels/sounds smoother cold or hot ! Remember I had previously 20w50 GTX Castrol and also when I got the car what the pre-owner used... I called the shop where the car was serviced with the pre-owners and they always use 20w50.

FWIW, Castrol GTX 20w50 Multigrade oil contains plenty of Zinc, above 1300 ppm to be exact, this is a more old school oil that I remember since the late 80's

So I believe I have plenty of Zinc plating formed on the engine surfaces and it will take me at least 10 000 miles to get rid of it...LMAO !! hey man to much Zinc can increase the wear ! cheers guys...

FredR

If your oil pressure gauge shows 3 bar at idle and 3 bar at 2000 rpm then in all probability there is something wrong with the sender or the wiring to the 14 pin connector. A warm 928 motor in good condition with 20w50 shows 2 barg at idle and about 5 barg by about 2800 rpms. The thinner oil flows through the main and big end bearings faster and the back pressure drops noticeably such that at idle it showed 1.0 barg in my case [and others have reported the same characteristic]- the oil is supplied via a positive displacement pump so the more oil that goes this way the less oil there is to feed the cams so a good reason to use 20w50. The thinner oil makes a noticeable difference to the engine pick up- not surprising as there is less resistance to motion thus why such oils can improve mileage

The ZDDP is in fact a consumable and the amount in circulation drops as the oil ages - the amount in the initial brew considers oil change intervals- but if there is not enough ZDDP in the oil the material sitting in the troughs of the metal surface will deplete. Racing oils can contain higher quantities but when the amount exceeds about 1600 ppm it becomes a corrosive menace and thus why in higher concentrations the oil has to be removed from the engine and thus not suitable for street use.

Wolfman928

I went to check yesterday, when oil nice and hot - it touches 3 bar bar at idle (in Neutral ) and goes back to 5 bar when driving away, just above 4- 4.5, when revving at 2000rpm as you come to a stop while driving it seems to drop a little lower, below 3...close to 2.5bar

when cold after start-up it read max (5 bar)