Daniel Dudley

I would have to agree with you that ZDDP is important for 32 valve cam lobes.

I won't consider an oil without it.

Leon Speed

In retrospect, a quote from Doug Hillary's LUBRICANTS FOR THE PORSCHE 928, 928S, 928S4, GT AND GTS: " Note that unless racing 10W-60 synthetic oils should NOT be used in your 928's engine"....

c_span

Yeah for this application I suggest that liquid sodium silicate stuff..

jon928se

We all have our own opinions. As I said earlier and reinforced by EW you need to look carefully at the viscosity figures and HTHS figures. Not all xxWyy oils are created equally.

JET951

That's a nice quote there Aryan but with no quantifiable data it means nothing. Has Doug done tests on a race spec engine with 10w60? or is it just a guess. Has Doug seen a race prepared 928?
I can tell you all from our personal professional experience from working on Porsche's for many years as a Porsche specialist here in Sydney, Australia... what works.
for 9 years now we have been competing 911's,944's, and 928's on the track. as well as regular servicing and repair of street Porsche's. In fact we just did a small write up in our Australian based 928 forum Beer Garden If you care to look
http://tinyurl.com/y9fg4jw
We pulled down a customers 1990 GT with 343,000kms. 213000miles. upon pull down(which was done because of oil leaks, Original engine, never opened)
We discovered that there was no wear on any component. not one item in the entire engine needed replacement because of wear. I do realise this is hard for many of you 928 owners to take in. The thrust bearing was within new spec 0.13mm. new spec is anywhere from 0.06-0.192mm. the ring gaps were all within spec. the big end bearings looked like new. the bores were perfect. and to our surprise we sent the heads away to our machine shop to get the valve guides checked and replaced if needed. with 343,000 city kms we expected valve guide wear. the heads were returned to us with new valve guide seals. the guides were all perfect and did not need replacing. The cams were perfect along with the cam sprockets and lifters, not a mark or pit to be seen.
We have known this particular 928 for a very long time and we know its history. It has been running Valvoline formula GP50 25w50 mineral oil, and now it runs Valvoline Maxlife as the replacement for Gp50. So my question to all of you running these thin synthetic oils is How do you expect to replicate this oil. How can you beat ZERO Wear? In fact Doug has even said that the Valvoline formula GP50 does not meet the requirements for the 928 engine, In our eyes We see this oil as a perfect match for our 928's. Unless you would like your 928 to wear our prematurely. (Formula GP50 was used by Official Porsche dealerships when these cars were sold and serviced here in Australia). but of course the choice is yours in the end Its your 928.

Marine Blue

Oil threads always seem to bring out the best in all of us.

Sean, to help others who are not familiar with the Aussie climate this car was running in, can you provide the details? Specifically what are summer and winter temperatures, was this mostly city and some highway or a mix? Was the car driven hard or babied?

Any additional info always helps.

Thanks.

Courtshark

Cheers to Sean. IMHO, nothing beats real-world data. Ever. However, Australia is subject to temperature extremes not seen elsewhere in the world. (I'm reading Bill Bryson's Down Under right now; hilarious travelog book). So, I echo's Afshin's request.

jon928se

I know the car and owner a little. It's a daily driver (Our commutes crossed in my old job about 2 times a week) No idea if it's been tracked.

Winter temps here - may get down as low as freezing one night in the year - generally early mornings will average about 10C Summer temps range up to about 40C max but a mean would be low 30s.

Having owned and driven the same 2 928s in the UK and here in OZ I can say with some authority that engine warm up times don't actually vary much between a 0C start and a 30C start - maybe 60 seconds until the temp guage shows a normal (normal being different between both my 928s) reading and no real difference until the oil pressure at idle shows it's normal hot reading. (This seems to take about 20 minutes of suburban/city driving regardless of temperature)

So I am a little sceptical of the generally espoused theories about ambient temps making a difference (Ignoring those few 928 owners living in Alaska or Death Valley/Red Centre)

Edit - in short my 928s run exactly the same here in OZ as they did in England

Marine Blue

Temperatures in the Northeast US and Canada can get very low and if the cars are driven or even started in the winter its possible to see increased wear with higher viscosity oils. Otherwise temperate is a small part of what can cause wear for most of our cars. Frequency of oil changes, how the car is driven, if it was tracked, has it ever been neglected etc are more important. Previous owners also have an impact. For example, if you happen to own a 5spd 928 which was previously driven by someone who doesn't know how to drive a 5spd, there is a very good chance you will have tranny issues and potential engine problems due to clutch in at stop light situations and redlining the engine during downshifts....

My goal isn't to debunk, its to add more information to this thread and learn.

For the record I'm using an 10W40 Synthetic and on a hot day in traffic the oil pressure will sit at 2BAR which I feel is too low. The car runs great otherwise and never runs hot. I am considering making a switch to a heavier oil but I'm on the fence. Threads like this can be helpful for those trying to learn and decide what to do.

Leon Speed

I agree - still waiting on Castrol to email me the specifics since some are not on the TDS.

I don't know, you'll have to ask him. I sent him a pm to ask if he could elaborate.

bogdan

Race engines use straight W50 ,W60, W70 oil. This oil is different as it has no polymeric compounds in it to alter viscosity. It is made to offer the best performance only above 100degC. FYI Honda's famous motorcycle racing engine RC350 peaked at 22000 rpm (yes, 22 000) back in 1963 and used straight castor oil!!!

JET951

Hi Afshin , I can answer that one , the owner of the GT we are talking about has been owned by the present owner for about ten years , I also knew the owner before that and the owner before that, and I can say it has not been babied but drived in the way humans do when confronted with a car that gets up and goes , in other words multiple owners who have used it ,with heaps of city work sitting at traffic lights odometer not moving engine still running , meaning the odometer would be higher if hours running is taken into consideration , and with other owners quite a bit of country / urban but and its a big but , this car has had regular oil changes for as long as I can remember and by the grace of god it has escaped the dreaded engine oils that have had wildly fluctuating ZDDP levels(usually too low as we now know) , particulary in the period 1998- 2008 .
We see two very different categories of Porsches at our independant Porsche workshop .

A) those Porsche's that have not escaped engine oils with very low levels of ZDDP, destoyed cams , lifter faces, excessive thrust bearing wear ,excessive valve guide wear, excessive cylinder/piston wear ,and most of these with less than half the mileage/ KMS of this GT mentioned

B) those Porsche's that have been running (from new) on a decent 20w-50 or 25w-50 with decent levels of ZDDP, and what have we been finding on these Porsches ?
Answer = nothing , meaning nothing needed / no wear .

Regards .BB.

Fabio421

Is there a way to by ZDDP in a bottle and just add it to your oil? I know you can do that with moly.

sharknoob

oppps

Rob Edwards

Torco sells a ZDDP additive called Zep: