Doug Hillary

Hi there,
Some time ago I agreed to supply oil condition reports for us all to learn from. And perhaps we can verify what Porsche recommend as OC cycles for our 928s
The first oil analysis report has arrived back from ExxonMobil and the results follow below

As stated in an earlier post it will be difficult to meaningfully measure wear metal trends due to;
a ) the the low vehicle use factors and,
b ) not having any reference material available on this subject/engine from Porsche

We will see any "unusual" elemental ( wear metal ) movements as/if they happen between the quarterly samples

Therefore, we can establish an oil change interval by monitoring its condition which is what this programme is all about

Vehicle = MY89 S4
Vehicle Speedo = 110112 kms
Oil distance covered = 6597 kms
Date Oil/Filter last changed = 17/10/02 ( about 5 months ago )
Oil = Shell Helix Ultra 15w-50 ( synthetic )
Oil topup since change = nil
Use = 10% Town, 15% Urban, 75% Highway
Avg Speed = 68 km/h
Avg Fuel economy = 12.1 ltr/100km
Temperatures = Highest 40C, Lowest 14C

Oil condition;

Viscosity - 94 - OK ( 58, much lighter oil though )
Water - 0% - OK ( 0 )
Soot index - 0.01 - OK ( .3 )
TAN - 3.2 - Ok ( NA )
The Total Acid Number ( TAN ) is an increasing measure of how the additive package is surviving
The Total Base Number ( TBN ) is the new oil's acid neutralising factor
Note: The TBN of the new oil is being tested today but is believed to be about 9.
The TAN should never exceed 70% of the TBN ( 6.3 )
( Note some comments are simplified for easy comprehension )

ExxonMobil's overall rating - "Normal" - excellent for continued use

For academic purposes the elemental analysis was;

Iron - 6 ( 19 )
Aluminium - 3 ( 5 )
Chromium - 1 ( 2 )
Copper - 3 ( 99 )
Lead - 4 ( 7 )
Silicon - 22 ( 9 )
Sodium - 5 ( 8 )
All shown as parts per million ( PPM )

We believe the high? silicon reading is due to the block's metallurgy

Figures for Mobil 1 10w-30 in a LS1 GM motor in the USA are shown in brackets. While these cannot be used to compare results it give some perspective to the figures in my 928 engine

I hope this is of interest. It shows so far that the oil has survived 5 months and varied use very well.

If anybody wants the one page doucument faxed to them just provide me your number with Country codes on here

Regards
Doug Hillary
MY89 S4
MY98 BMW Z3 2.8
MY02 Subaru Outback 2.5

Russell82

Outstanding, will be watching for future reports. I am amazed that when I change oil on my 82 Auto at 3000 mile intervals, what comes out of the pan is almost indistinguishable from new - no black, no crud, no particles noticable at all. Granted they hold a lot of oil, and the 3K interval is probably a little obsessive, but the apparent cleanliness of my old oil suggests quality metallurgy and tolerances that far exceed any other auto engine I've owned.
RAS

Jim bailey - 928 International

Doug so after about 4,000 miles your oil was evaluated as "normal excellent for continued use" That may help support why Porsche recommended 15,000 mile oil change intervals . It also reinforces my comments that changing oil every 3,000 miles is obsessive and if you are a business and encouraging consumers to do that so you make a profit borders on being criminal. Even Jiffy-Lube has modified what the windschield "reminder" sticker says . It now says simply "Return for service" receive $3.00 off if you return within 500 miles of mileage shown below. No mention of " scheduled ,recommended "etc. just a discount ...the legal department has been busy .