Doug Hillary

Hello,
this is a Used Oil Analysis (UOA) of Mobil's Delvac 1 5w-40 Heavy Duty (HDEO) commercial diesel "mixed fleet" oil used in my ‘89 S4 over the last several years
It is UOA Report No 12 and it will help to enable others to compare their own UOAs for trending purposes. This is the final UOA from me on this vehicle as I have replaced it with a Boxster. The 928's new owner will be encouraged to carry on the practice

Details:
Car - MY89 - 928S4 Auto
Speedo - 96984 miles (156174 kms) now
Oil - Mobil's Delvac 1 5w-40 fully synthetic HDEO - API rated as "CI-4/SL"
Oil & filter change date - 11 Aug 06 (OEM "MANN" filter used)
Distance since Oil & filter changed - 3703 miles (5964 kms)
Oil used since 11 Aug 06 - nil (still at "FULL" mark)
Date of this sample - 9 June 07
Distance since last sample - 3703 miles (5964 kms)
Use in this period - 10% town, 20% urban, 70% highway
Avg speed in period - 50 mph (80 km/h with a highest speed of 220km/h)
Fuel economy in period - 12.1 ltrs/100km
Ambient in this period - +42C high to 5C low
Humidity in this period - 98% (highest)

Oil Condition after 10months use; OK for continued use

Viscosity OK - 84 (excellent) [88] Average of all at Oil change (Virgin oil is 92)
Water OK - 0.00%?
Sodium OK
TAN OK - 3 (excellent - lowest is best, max allowed is 9)

Lab. UOA Report Summary;

ExxonMobil's rating is "Normal"
Translated status "Excellent - suitable for continued use"
Last Report "Normal"

Elemental (& wear metal) Analysis (in parts per million - "ppm");
Details of the following columns;
Column 1- current UOA result (my comments are in brackets)
Column 2 - [?] rounded average of all UOA results at oil change

Iron 7 (excellent) [11]
Aluminium 3 (excellent) [5]
Chromium 1 (excellent) [1]
Copper 2 (excellent) [3]
Lead 3 (excellent) [7]
Silicon 4 (excellent) [5]
Sodium 4 (excellent) [5]
SPECIAL NOTE: The averaged figures are a good baseline for any 928 owner of a non tracked road use vehicle to use for comparison purposes

NOTE 1: General summary

This UOA result is typical of all of the previous UOAs. All lemental wear metal readings are at or below the previous averages for this engine and well below Industry acceptable limits

The full series of twelve UOAs taken at various distances, indicate that the rings, pistons, bores, cams, cam, rod and crank bearings, crankshaft thrust washers and other major components are all wearing at a very low rate indeed

The oil testing done to date justifies using Porsche Approved and Listed (or better) oils at the Listed viscosity. It confirms that following their recommended servicing intervals is cost effective

NOTE 2: Oil performance observations (Delvac 1 5w-40)

A - Oil viscosity
A 5w-40 viscosity (the current recommendation) oil seems ideal for year round use in a 928!

B - Wear metals
The Porsche recommended 5w-40 viscosity oil has maintained the lower trend in engine wear rates
It should be noted that wear metals will increase in volume (in ppm) until eventually drained with the oil - they are simply too small to be filtered out. The averages shown above are only from those samples taken at the oil change point for this very reason

NOTE 3: Current oil condition summary

Delvac 1 5w-40 has again performed very well and using in a 928 gives plenty of reasons to feel confident that we "caught the right tram"with this lubricant! The oil still has near new viscosity and its ability to combat deposits and acids remain very high indeed

It is worth noting that by tracking both the oil's condition and the rate of wear metal(s) uptake the following data emerges;

a) the premium synthetic oil will last for at least two (2) years and probably three (3).
b) The Sodium "action" limit would be reached theoretically at around 90k kms
c) wear metal uptake rates indicate that the oil would theoretically last up to around 80k kms before any "action" limit is reached
d) the MANN oil filter will easily last for at least two years or 50k kms

I do not advocate going beyond 12 months without changing the engine oil/filter in a normally used 928

I hope this is of value to those Rennlist people who want to maintain a condition history and also "keep an eye" on thrust bearing and other wear/failure points in the 928 family of engines

Regards

AO

Doug-
Thanks for posting this installment of your UOA reports. I think the timing of this is perfect as a few of us have recently changed to other brands/viscosities of oils. Obviously the condition of the oil you are using seems to indicate that everything is happy in the engine.

As you know I recently switched from Castrol GTX (10W40 IIRC) to Shell's Rotella T (Full Syn) 5W-40. I found on a hot day (90+F) in Michigan, my oil pressure struggled to get above 3 bar. This was a bit too scary for me as the FWSM says I should experience 5bar at 5k RPM went he oil is between 80c and 100c. I have since switched to Mobil 1 15W40 (or was it 15W50??) and everything seems much happier.

Out of curiosity, with the oil you are running, can you give a brief report on your oil pressure readings? Also, how do you drive your 928? Short trips vs. long trips? Aggressive, Spirited or casual driving? I think these other factors play into how the oils and the engine interact and can help the rest of us make the best possible choice for our cars. Thanks.

Doug Hillary

Hi Andrew,
some answers for you

Driving style
I never abuse a cold engine by using high revs (keeping revs below 3k until 80C coolant temp) and my driving style could be described as spirited.
My car saw 200kmh (120mph) for short distances at least once per week on average
Many of my trips are/were long and at a high speed - the last one was 1200kms (750miles) at an average of 103kmh (65mph). I do not live in a large town and we had our first set of traffic lights installed a couple of months ago. I live in the Tropics where a constantly high ambient and high humidity is the norm

Oil pressure
The following data covers the last five years - the oil temperature was always above 80C
when OP was recorded

Castrol semi synthetic 10w-40 (from new pre-delivery to 100kkms)
At 100k kms;
Idle - 2.5-3bar
@2000 - >4bar

On Shell Helix Ultra 15w-50 (fully synthetic)
Idle - 3bar
@1400 - 4bar
@1800 - 5bar

On Delvac 5w-40 (fully synthetic)
Idle - 2-3bar (I have seen 1.5bar in very high temps/after high speed)
@1400 - <4bar
@1600 - >4bar
@2000 - 5bar

My recording are off the inaccurate OP gauge and most others in OZ that use Delvac 1 5w-40 report about the same OP readings

As a matter of interest Porsche factory Workshops here appear to use a 15w-40 HDEO semi synthetic oil in all pre 1984 engines

Regards

AO

Thanks Doug. That's very interesting. One would think that there shouldn't be such a discrepancy between our cars, but ovbiously it appears there is. I agree the factory gages probably are not the most accurate, but I find it hard to believe that they would be off that much. I'm not sure I want to investigate this much further. I may look at replacing the OP sending unit, but that's about as far as I may go with this. Thanks again for your report and follow up data.

Doug Hillary

Andrew;
this comment from a friend (and Rennlist Member) regarding oil pressure may be of interest;

"If you have a digital dash (But I don't see what year / model your 928
is) then you can test it easily by bridging pins 5 and 13 on the big
round 19 pin plug (the one beside the passnger's seat)."

He found that his gauge was reading about 1bar less than actual off the digital readout if I recall correctly

Where are you Dave O??????????????

Regards

AO

Thanks Doug... I forgot about that. I believe this can also be tested through the digital dash diagnostics. It appears that you can even make an adjustment... I'll investigate further tonight or tomorrow.

Jim bailey - 928 International

Doug Thanks for all the REAL data on the 928 oil life. I hope you enjoy your Boxster !

F451

x 2!

daveo90s4

Ah Doug my friend, I'm here, lurking.

Your recently stated maximum of 220 kph - would I be right in thinking I know exactly where that happened??!!

And Andrew, yes Doug is correct my oil pressure gauge does indeed read 1 bar too low at a stated 1.5 bar and 0.5 bar too low at a stated 4.5 bar. Recalibration is very very simple - same method as recalibrating the temp. gauge (once Doug Hillary showed me how check using an IR gauge). - remove pod, pull needle, replace needle in correct spot. Easy.

Boxster eh Doug. That's interesting, the guy I bought my 928 from was selling to get a Boxster. Let me know your thoughts. david.overington@rta.ae

Cheers

Doug Hillary

Hi Dave,
sure miss your company!

OT - I miss my S4 already and seeing it for sale at Porsche Center Brisbane today was not a good trip! I'm in Brissie tonite but will have to miss the Brekky Creek deal as I'm entertaining Son 4 and partner - I bet you wish you could be there too!

You'll remember my Airlie Beach "test tracks" well no doubt - but our Bris-Syd was a great one as well

I'm meeting Bruce W & Janne for dinner in Townsville on 28/7

Please keep in touch

Regards

unit

Hi Doug,
Did you trade in the 928??
If your selling it please let me know.
Sam.

pasa

Hi Doug,
I sorry to hear that you sold your 928, I hope you keep popping in on the 928 forum , your information on engine oils is invaluable it has helped me out tremendously. Thanks and enjoy your new Boxster .

Dan 1990 928GT

hinchcliffe

Shell Rotella Syn 5w-40 on the OP gauge is 2 bar at idle hot. Pegged at 3k rpm, when it is 90 deg F outside at idle it dips to 1.5 bar.

When I ran Mobil 15w-50 it was 3bar hot at idle. Pegged at 3k rpm

When I ran Amsoil 20w-50 was about 3.5ish bar at idle. pegged at 3.5k rpm

mark kibort

We just did this test with scots, and of course, the holbert car is a living testimonial to Amzoil. 20-50 amzoil gets pegged at 2500rpm. when im racing in 100F temps, that grows to 3 bar. mobil 1 had a hard time EVER reaching "pegged" when racing hot. in fact, it started to fall so bad , i was getting oil pressure warning light.

In scots motor, a change of oil and the same hot operating temp brought the oil pressure up to 5 bar at 1000rpm less than with Mobil 1.

I have another sample of my used amzoil racing oil that has been sitting for a couple of months in the mailer tube. Im going to send it in and see what it shows.

Mk