Doug Hillary

Hi,

This Oil Condition Report ( Used Oil Analysis - UOA ) relates to the current oil in my car and may be of interest to those who have followed the previous five reports over the last year or so

The oil and filter were NOT changed at this point as ExxonMobil's Lab. report OK'd the oil for continued use. It will be changed at Porsche's prescribed maximum time limit

Mobil's Delvac 1 5w-40, a synthetic commercial HDEO ( heavy duty engine oil ) with both diesel/petrol ratings is being used and this is the second UOA on this lubricant
This is the latest API rated "mixed fleet" diesel engine oil - CI-4/SL - and it also exceeds ACEA's A3 and B3 ( E3,4,5 & B4).
It is suitable for high performance petrol engine vehicles and meets the car's viscosity requirements

Details:

Car - MY89 - 928S4 Auto
Speedo - 125214kms ( 77758 miles)
Oil - Mobil Delvac 1 - 5w-40 full synthetic - API rated as "CI-4/SL" **
Oil/filter change date - 10/07/03 ( OEM "MANN" filter used )
Distance since oil/filter changed - 8130kms ( 5049 miles) Time since oil/filter changed - six months ( approx )
Oil used since oil/filter change - nil ( still at "FULL" mark )
Date of this sample - 3/9/04
Distance since last UOA - 2695kms ( 1674 miles ) Time since last UOA - three months
Use in this period (approx ) - 10% town, 30% urban, 60% hiway
Avg speed in period - 61km/h ( 38 mph)
Fuel economy in period - 12.2ltr-100km (23 mpg Imp) ( 19.5 mpg US approx )
Ambient in this period - 40c high to 18c low
Humidity in this period - 98% highest

** This oil far exceeds Porsche's original API rating recommendations for the S4 but meets the original viscosity requirements

Oil Condition - "use" factors;

Note - UOA report figures:
Viscosity OK - 86 ( excellent )
Water OK - 0.7%
Soot Index OK - 0.01 TAN OK - 3.5 ( excellent ) Max allowed = 8.9

Lab. Report Summary

ExxonMobil's rating now - "Normal"
Status-Excellent for continued use
Last Report - "Normal"

Elemental ( & wear metal ) Analysis;
Detail of the Elemental columns are:
Col 1 = this UOA ( my comments in brackets )
Col 2 = averages of all six UOA's
Col 3 = Oil Industry's "acceptable" max. wear rates (rounded) & not 928 specific

Note:

None of the elemental wear rates are really significant. All are around the previous averages and well below the Oil Industry's maximum acceptable figures. This indicates that rings, pistons, bores, cams, bearings and other major components are wearing at a very very low rate
This is another "technical analysis" of why the 928 engine is so durable in normal use when using the Porsche recommended ( or better ) lubricants that are changed at Porsche's recommended servicing intervals

Oil Condition Summary:

The oil has been used for 8130kms ( 5049 miles) in about six months. During this time the car was driven above 160km/h ( 100 mph ) for extended periods in 33+C temperatures

This very high quality oil will be changed according to Porsche's distance/time recommendations or earlier if the June UOA determines this - which is most unlikely!

Regards :cheers

slate blue

Well done Doug! Thanks for going to such trouble, I have always thought what has killed the 928 motors has been contamination, either dirty air or oil. With quality lubricants and good maintance the 928 engine should be good for hundreds of thousands of kilometers. Incidently I used to run a mobil diesal oil back in the eighties in my Holden 202, it used to run like a dream. I suppose being a diesal mechanic had the word on their superior oils.

Lagavulin

As always, nice report Doug!

Garth S

Second that, - an excellent, continuing study!
Clearly, an engine in good health, using good lubricants can continue to do so for many thousands of Kms prior to change out This is born out in numerous fleet lubricant studies.
This has to challenge( with facts) the sales line in many used car ads, "Mobile 1, changed every 3000! in most cases, overkill.

Old & New

Doug,

A hypothetical question for you, assuming that oil is like new after 6000 miles:

If a car uses a quart every 800 miles, and the oil is only topped off but never changed, how long would the oil remain within specifications?

Gretch

Doug, Nice to hear from you again on this subject.

FWIW, you have a convert here. I have "converted" my diesel fleet (2 big farm tractors) to the delvac 5 w40 - I finally found a source for it. The rest of my fleet (2 P cars, A6 twin turbo, hunting truck, Harley and 2 honda ATVs) run mobil 1, either 0 w40 or 15 w50. Like I said. even the hunting truck gets synthetic now, as I dont keep dino in the shop any more. This is all your fault, and I sleep better for it.

Thanks again.

Jim bailey - 928 International

Old and New... in the previous well documented study Doug has shown that at 15,000 miles his oil was still well with in specifications ...........in your car using a quart every 800 miles you would have ADDED 18.75 quarts of oil in 15,000 miles ........ it gets you into the realm of the 200 year old soup sold in some chinese restaurants every day they just add more ingredients and keep on cooking . Doug has done more than anyone I know to disprove the MYTH that oil needs to be changed every 3,000 miles or that doing so is being good to the engine . He was unfairly criticized by some for his initial comments and decided to PROVE what he already knew to be the case . So at this point in time his is the only well documented publicly disclosed FACTUAL report about what happens to oil in a 928 engine . It is also no surprise since Porsche recommends changing oil at 15,000 miles (or sooner under certain conditions like short distances , stop and go , very dusty BUT says nothing about FAST or high RPM ) .

Old & New

Jim,

As you can probably figure, I'm suggesting that if you are adding 2.5 times the capacity within the recommended change interval, then what is left in the crankcase would probably never go out of spec.

"Update to GTS owner's manuals: Never change your oil!"

Garth S

Well, almost: add,........ " - but change the filter every __ Kmiles"

Doug Hillary

Hi,

thanks to all for the comments I'm pleased there is some value here for all of us in the 928 fraternity

Gretch - well done the benefits are yours!

Old & New - Jim's pretty much on the money!

Oil gets dirty and primarily has to counteract acid build up. If you can counter these issues you could and can use oil indefintely. This is done in some marine and other industrial applications like power stations

In the automotive sense the top up rate definitely assists the oil by restoring part of the additive package. The real trick is to get this top up rate right. Cummins Diesel have done much work on this issue over several years and have engines in the field that burn oil at a set rate with an auto top up device. One of my customers has had a number of their engines successfully running in remote road train work like this for about two years

If you read the thread here titled "By-Pass Filters", by Paul, you will see that their are other ways to keep engine oil clean ( cleaner ) too

In the coming decade or so you will see new vehicles with engines that are "filled for life". They will have perhaps a throw away or cleanable oil conditioner package fitted to the engine. This will include a centrifuge, FF filter screen ( for the big bits ) and will use advanced synthetic lubricants
Electronic engine oil monitoring via the ECM is already being done and this will determine the actual cleaning interval according to fuel used and climatic circumstance

In the meantime if you have an engine that uses a lot of oil, regular UOA's would certainly determine the optimum oil drain point which may be way beyond Porsche's normal. The filter being replaced normally of course!

As a matter of interest this whole 928 & UOA "thing" came about 12 odd months ago because of a question just like yours

And, as long as 928GTS owners ( lucky people ) keep an eye on their sump's oil level using the dipstick, and the correct oil ( ( 5w-40> ), they should easily reach Porsche's recommended drain intervals!

Regards

Rich9928p

Thanks Doug!

Facts and analysis are a rare commodity on the internet.

Perhaps a group of interested people could underwrite a test of Mobil 1R in my '79 Euro track beast.

However, my oil capacity is now in the 11 quart range since I have added a 3-qt. accusump and plumbing. I'm doubtful that one season of activity would stress the oil. I added an oil temperture gauge to be sure that I never get into the trouble zone.

Doug Hillary

Hi Rich,

like you no doubt I am still waiting on meaningful UOA's on M1 R

You will be cautious of flow and pressure I'm sure and the oil temp gauge will be a great help here. The extra 3-qt oil capacity will be a real plus too allowing more cooling etc.

Rich - what is the ACTUAL oil consumption of your GTS and what oil do you use in it?

Regards

Rich9928p

"Rich - what is the ACTUAL oil consumption of your GTS and what oil do you use in it?"

My GTS is now about 45,000 miles. It has gone as far as 4000 miles on one quart of oil. If I run it real hard, that will drop to 1 quart in 2000 miles. I change the oil at 7000 miles or one year, so often my changes have been time rather than mile driven. I've always used Mobil 1 15W-50 oil.

My track car may use 1/2 to 1 quart of oil (Mobil 1 15W 50) in 2 - 3 track days.

As a side note, I lived in Germany in the mid-80s. I would use a company car (Mercedes 2-liter mid-size) for company trips. We would drive those things wide open for hours (~ 170 kph). The oil consumption was easily 1-liter per day at those speeds/RPMs. The Germans never thought anything of it. I think any engine will consume oil when run near/at redline. We don't do a whole lot of that in the US with our low speed limits.

Doug Hillary

Hi Rich,
as you probably know I lived in Denmark for many years and travelled to Germany very often. I have spent lot of time in Germany too mainly with MB

I totally agree with your comments - people get alarmed with any use of oil at all. The Germans have always been careful to publish oil use factors for that very reason

I am sure you will lose oil pressure ( and gain flow ) with the M1 R and I will be very interested to see what your idle pressure is and the running temperatures. Please publish those for all to digest

Both of your cars have very reasonable oil useage

Whilst I do not use M1 ( my wife's Golf uses M1 0w-40 ) I believe the SuperSyn M1 15w-50 is the best value synthetic of them all

Its sold here as a 5w-50 and is the most popular oil amongst 928 owners

Kind regards