sendarius

I have never found Mobil1 15W50 on the shelf anywhere in Perth, but the distributor in Welshpool can supply it in 5 or 20 litre containers.

Take a look at Statewide Oil, 14 Beete Street, Welshpool.
http://www.statewideoil.com.au Ph: 08 9350 6777

jcorenman

There's not a 50w on those pages, and you live in Phoenix?
The heaviest base on that list is 5W40, your owner's manual limits 10w40 to 90F. What's your max summer temp?

Here's my take: The 928 was designed by engineers, before accountants took over the company. (That's why it is a great car that didn't make them much money). The oil requirements in the owners manuals reflected the engineer's design specifications. Porsche's current oil recommendations are aimed at the more recent engines, and --how do I phrase this politely-- engine longevity may not be among the company's highest goals.

My strong suggestion is to run a routine oil analysis, costs $28 per oil change which is a minor expense.
Info: http://www.blackstone-labs.com/
Look for ~1ppm lead per 1K miles, that is normal bearing wear. Copper <10ppm, ideally around 5, that comes from worn bearings. Any significant alum or iron (>10 ppm) is trouble.

Run 15w50 or 20w50 with at least 1100 ppm zinc (ZDDP), Blackstone will also do a virgin oil analysis for $28 which is cheap insurance. Most 5w40 or 10w40 will not have adequate zinc levels.

Bucko74

Thanks for the help, and I will give them a call tomorrow.

I needed an oil change, so settled on Shell Helix HX3 20w-50 for now. I'll give this a run given its the correct viscosity for our temp ranges (as per the manual).

I'm sure I've seen one of your S4's driving around recently. Didn't notice the Cayman mags though.

TheoJ

I use 10w60 or 5w50. Castrol brand, or LiquiMoly. Additional ZDDP at each oil change.
The oil pressure is still good when the engine is really hot. The 5w50 tends to make the tappets louder when starting cold.

1992 928GTS
Theo Jenniskens

marine928

I just received my oil analysis kit from Blackstone. I will change my 15/ 40 Lubriguard Tuesday 01/10/17 and send it off. Current milage at oil change will be approximately 6690 miles since last change on 06/18/16.
I will also send a "virgin" sample of the Lubriguard and compare. Will post results when I receive them.

https://pqiablog.com/2016-motor-oil-samples-tested/

https://pqiablog.com/2015-motor-oil-...side-by-grade/

http://www.pqiamerica.com/viscosity.htm

http://www.pqiamerica.com/calcium.htm

ptuomov

First, what does the virgin oil analysis tell us [about ZDDP]? Does it tell the phosphorus ppm and zinc ppm individually? Or the ZDDP ppm? If it only tells us the elemental concentrations of phosphorus and zinc separately, then how does one reliably infer the ZDDP ppm from those?

Here's one ranking based a specific oil film strength test (not the final/word complete-answer test, just one test, but probably better than nothing) for "high-zinc" oils:

http://www.speedtalk.com/forum/viewt...art=15#p477109

Second, why is the high (hot) viscosity oil, higher than what the factory recommends, better for 928s?

marine928

I just want to compare the Black Stone virgin results with the manufacturer's claims.

worf928

Posting this for all the newbies (although this is old enough that perhaps even 'medium-ies' have never seen it on the front page) :

LUBRICANTS FOR THE PORSCHE 928, 928S, 928S4, GT AND GTS

worf928

Another good reference:

Tech 101: Zinc in oil and its effects on older engines

jcorenman

Science always needs a baseline Running a VOA provides a baseline for interpreting subsequent test results. For example, silicon is typically a contaminant (dirt getting through the air filter) but some oils have a few ppm silicon as an anti-foam, nice to know. Brad Penn uses sodium and magnesium as additives, as well as calcium-- so when those show up, no reason for concern. It also gives you a starting viscosity, so you can have some measure of how much the oil is getting beat up-- or whether it was just thin to start with. Some are better than others.

Phosphorus and Zinc are listed separately, my understanding is that the ZDDP level will be somewhere between those two values. A recent Brad Penn 20w50 sample shows phos at 1198, zinc at 1336, and I believe the ZDDP spec is 1200.

Oddly, LiquiMoly 10w60 showed only 733/824 for phos/zinc, so ZDDP would be somewhere around 800-- that seems marginal for these engines. Porsche Classic 20w50 was also on the low side: phos/zinc was 838/818.

As for viscosity I don't have an answer. My owner's manual shows 20w50 for moderate through unlimited high temps, so that's what I've always used. The 10w60's that I've tested (LiquiMoly and Porsche Classic) were quite a bit thicker at 100C: 22 and 23 cST respectively, versus 18-19 for a 20w50. Thicker is not necessarily better.

ptuomov

What are your thoughts on Liqui Moly for a forced induction street 928? Liqui Moly 10W-60 Racetech GT1.

https://www.liqui-moly.eu/liquimoly/produktdb.nsf/id/en_1390.html?Opendocument&land=de&vcmstemplate=mobile&redirect=1

I'm thinking it should protect well in cold starts given 10w, about 1000 ppm of Zinc, and other cold-start wear protection compounds. Then when hot it should flow about the right amount while protecting parts adequately.

Also, isn't ZDDP something that gets consumed by cold starts and metal to metal contact? That is, as long as there's a high enough concentration which may not have to be very high at all, the extra ZDDP is just going increase the required oil change interval? That's a question, not a statement: I don't really understand all these issues as well as I'd like to.

ptuomov

I get the general baseline point. Was interested specifically about ZDDP.

The info from manufacturer for that Liqui Moly oil is 970-1150 ppm of zinc.

I think that company started as a maker of various molybdenum lubricants so I wouldn't be shocked if their anti-wear package has a lot of that. The "problem" is that I believe all these oils we're talking about here are so good that it would take a really long time to see any practical differences in actual differences in engine wear.

Thicker at 100C is indeed not always better. My logic (not facts) is the hot viscosity of the oil in the 928 engine will mostly impact the flow rate, holding the pressure test rating constant. Do we want a high flow rate or a low flow rate, what flow rate is just right?

jcorenman

Hmmm... My sample was a couple of years ago, if you are planning to use it then I would grab a quart and send a sample to Blackstone.

Zero.

Do turbochargers have any special lubrication requirements?

Mikebte

I live at high altitude not far from Phoenix. High of 85 in the summer, and this year my low has been 30.
But I don't always drive it in winter.

I'll have to look up the Blackstone. I have never used them

I use to run my own oil analysis when I worked for a company owning the equipment. Was sad to see my changed oil was never even close to broken down.

And for the folks in question. Bankers do run most companys. It is a great idea to ask questions and do your own research. For instance,
When I worked for Cummins, they had approved light weight synthetic oil 5W-40 in its ISX engine line. Semi truck engine. At random intervals they had started loosing camshafts and bearings.
We would all like to think they would issue a TSB and fix the issue, but they did not.
They simply replaced the cams that broke under warranty and let it wash under the table. The next year they switched to Valvoline Blue, had them build the oil (Valvoline Blue) and no longer recommend synthetic.

So it is vital to do research and have your own knowledge of oil, and always be willing to listen to others knowledge. The auto industry is no longer on our side.

ptuomov

Some of them may have, if they have oil cooled journal bearings.

I've got ball bearing turbos that are cooled with engine coolant, and an electric auxiliary water pump and an electric oil scavenge pump that run for a period after engine shut down, so I'm thinking that these turbos don't put any additional requirements on the engine oil. Just based on common sense.

Of course, the higher heat and additional load from making more power add to the oil requirements but not directly in terms of turbocharger lubrication. Common sense tells me that the oil will likely run hotter if the rod bearing loadings under compression are three times higher than stock and the engine makes three times as much power. That's why I'm kind of thinking that SAE 60 hot viscosity might be the right pick.