JET951

The deep last century Porsche 928 series ( all including the quad-cam engines ) are known as "High Loaded Flat Tappet " design , meaning the wiping loads on the very pointy cam lobe/s combined with the strong double valve springs holding the hydraulic lifter ( face/s ) result in a lot of stress for the cam lobes and consequently the hydraulic lifter faces . ( No roller rockers in these engines )

Note 1 } There is NO oil pressure at this point where the cam lobes contact the lifter faces , the cam lobes and lifter faces only receive oil splash feed & hence require a "High Oil Film " strength engine oil to survive ( prevent cam lobe wear ) , that's because lower oil film strength oils ( low viscosity so called synthetic with low levels of ZDDP ) is simply wiped away & it becomes metal to metal contact without the oil film strength keeping to two metal surfaces away from each other

Note 2 } The only oil viscosity that's recommended by the people at Porsche ( last century ) who built the 928 & is actually printed in your owners manual that came with every 928 1978-1995 ( oil viscosity page ) , it shows quite clearly that from minus 10 deg celcius to unlimited high ambient temperature , in the shaded "Look at me section " of the owners manual , first oil on that list is = 20w-50

Note 3 } Last century oil viscosites for last century engines are made and sold just for last century engines for a reason , and off the shelf oils sold to the public , the 20w-50 engine oils generally have much higher "Oil Film Strength " than a this century lower viscosity so called synthetic engine oils , like a 5w-40 & even worse a 0w-40 ends up badly in a last century Porsche engine , partly because of the said cam wear , but just as importantly when the engine oil is at operating temperature ( 85 to 95 degrees celcius or higher , particularly when driven hard ) at these normal operating oil temperatures at high engine RPM the oil pressure within the crankshaft going to no 2 & no 6 con-rod bearings ( big end bearings ) will starve / insufficient oil pressure and destruction of the 2 & 6 crankshaft journals can and most likely occur & the hotter the oil the lower the oil pressure , hence why over the decades we have seen countless 928's ( all year models ) , 944 ( all year models ) , air cooled 911's ( all year models ) turn up at our workshop ( first time with this owner ) with the oil pressure warning light glowing "RED" at idle , meaning insufficient oil pressure at idle with engine oil at operating temperature . Switching back to a 20w-50 ( like it says in the owners manual ) instantly rectifies the "Glowing Red Oil Pressure too Low " light ( providing they have not already damaged / excessive wear of the engine con-rod and even main bearings by running on the thinner oil viscosity )

And talking about the 928GT , late 2019 we dismantled a customers 1989 year model 928GT engine ( 180,000 or so Kms from memory ) and we dismantled it because in old age it was leaking oil from every gasket and seal & we wanted to replaced the head-gaskets before it was too late , but the thing that struck us here was the condition of the GT cams ( all 4 of them ) , they are similar to the 928S4 cams but ( from memory ) have an extra 1mm lift and naturally these 928 GT cams are well known around the world to suffer cam lobe wear , but this engine was a little unique as the owner had been very aware of the issue using ( we call it experimenting ) with this century low viscosity so called synthetic engine oils in deep last century engines and kept his 928GT running for decades on a 20w-50 , the GT cams in this engine were in ( for want of a better description ) new condition , there was not only no wear , it was difficult to see that there was minor wear on the hydraulic lifter surfaces , it was a Wow moment .

In regards to last century Porsche engines I / we have only seen cam wear and the corresponding lifter face wear & crankshaft thrust bearing wear when the said engine was on a this century low viscosity so called synthetic engine oil , particularly a 5w-40 and sometimes 10w-40 & I have been working on Porsche cars for 46 + years

Something to think about , at idle ( say ) 750 RPM every valve ( inlet and exhaust ) is opening & closing 6.25 times per second ( 375 times per minute ) & at ( say ) 6,000 RPM the valves are opening and closing 50 times per second ( that's per second ) , that equals 3000 times per minute , no wonder with high loaded flat tappet design they need a lot of protection = High Oil Film Strength

Regards
Bruce Buchanan
Buchanan Automotive
Sydney , Australia

Strosek Ultra

The low viscosity oils of this century are designed to reduce emissions and save the world from climate change. Now that we will soon all be electric, this is a non-issue.
Åke

Darklands

The new Q3 from my wife uses 0W20

The high ZDDP in the Oils from the 80ies wasn't good for the catalysator, the same as lead in the fuel.

Strosek Ultra

I refuse to have catalytic converters on any of my eight cars.
Ich weigere mich, Katalysatoren an einem meiner acht Autos zu haben.
Åke

Strosek Ultra

Any pittings on the cam lobes?
Åke

Fly911

It looks like the most of us agree that the 20W50 grade with high ZDDP is the correct oil for our beloved cars. When it comes to the brand, I believe it's more a "religion" with strong believes, rather than actually big differences between the otherwise same grades of oil. I have no doubt that the Valvoline VR1 Racing would be excellent for my S3, with spirited and occasional redline driving.

When it comes to oil change intervals, I believe that we should change once a year, pretty much independent of driving distance. I also believe that none (or very few) of our cars are reaching the max recommended change interval of 10k or 15k miles.

When it comes to ZDDP and catalytic converter damage, who gives a F...? Obviously none of our cars have OBDII, and in most states there are no requirement for emission testing for cars more than 25 years old (except for the Socialist Republic of California). Many of us have cat delete and X-pipes installed, so the ZDDP does no harm.

So would that make our cars pollute more? NO!!! My car don't pollute more than the average Prius that is driven 15k miles a year (assuming I'm driving 5k miles/year), and way less than all the F150's, Silverado's and other trucks and SUV's. So my loss of sleep for taking off all the emissions devises (including cats) is zero.

Strosek Ultra

This is what can happen with the wrong oil and/or lack of lubrication. It's a BMW six SOHC with rocker arms.
Åke

zaevor2000

Since changing engine oil is performed regularly by us 928 owners, shouldn't this be made a sticky?

It is one of the most CRUCIAL decisions you can make in maintaining it and I personally would like to see it stickied to a place where old and new owners can see it since it is performed more often than any other car maintenance activity I can think of.

Our cars have been out of production for many years and the drivable ones are becoming fewer and fewer with each passing year.

We owe it to all to give the best information possible to keep as many of them on the road as possible.

I myself would HATE to be guilty of giving advice to a fellow owner that is not in their best interest.

I want to be able to instantly point them in the right direction for the right advice on their cars.

We have a GREAT hive mind in our section of Rennlist and would like to see the wise guidance and experience of many of the great owners given the visibility it deserves...

UpFixenDerPorsche

Now why would you say that?

928 GT R

FredR

By any chance did you ever see the cam tower video my dear friend Louie made whilst developing the beast you now have the privilege of owning?