rmoleman

1986 951
60,000 miles
Second owner
Street car
Mobil One

How long do you go between oil changes?

I have been going ~5,000 miles between changes which is sometimes 5+ months if I do not drive much. The used oil comes out looking like new oil, so i was thinking of going a little further.

LFA951

That's fine, I change mine every 3,000 or 3 months, whichever comes first and I use regular Dino oil Valvoline VR1 20W50

rdanford

I've had this discussion on other forums before and I'm still a 3,000 or 3 month kind of guy...I use Mobil 1 in the Porsche and Royal Purple in my other cars/trucks...

ehall

if you're not putting on many miles AND it's coming out like new then you're doing fine. You could do 5k on a daily driver if you wanted to. Synthetics hold up awfully well these days.
I will say that you might want to switch to the Valvoline Racing synthetic product. Do a search about oil and you'll find a thread on this bored about the new oil standards. Valvoline is about the only moderately priced product that is using the old standard, but if you are already paying for M1, (which is using the new crappy standard) you may as well use a better similarly priced product.

GOBOGIE

3,000 or every summer like I do as I take about 2-3 years to get 3,000.

Luis de Prat

If you do a search on this you will find that changing full synthetic at 3K mile intervals is pretty much overkill and a waste of resources.

An Australian fellow on the 928 board did some research on this, having the Mobil1 full synthetic oil in his 928 analyzed periodically up to something like 30K miles and the lab analyses showed that the oil maintained its viscosity and lubricating properties well enough throughout.

Only thing worth replacing more frequently than the oil is the filter. YMMV

turbo8

ya that 3000 miles or 3 months was long ago when oil wasnt as good as it is now, the oil companies still tell you to change it at 3k or 3 months. there product they can say what they want.

if its a daily driver it should be fine til like 7500 miles, i still like to change my oil between 3-5k depending on driving and conditions, makes it feel like it runs better, placebo(spelling?) effect? maybe :-)

Luis de Prat

Here, I've compiled the reports for your review. The results speak for themselves.

01-27-2003, 08:52 PM
In response to comments from "Marc@DEVEK" I will commence a programme forthwith to sample the engine oil in my car a MY89 928S4
ExxonMobil have agreed to sample my oil as follows;

1 - new Shell Ultra Synthetic 15w-50 ( SJ/CF-A3 Porsche approved )oil sampled as baseline

2 - current oil in crankcase ( same batch Shell Ultra Synthetic 15w-50 ) will be sampled within the next month @ 7 000-8 000 kms of use
To enable accellerated results I decided to remain with my present Shell oil rather than move to Mobil 1 5w-50 or Mobil Delvac 1 5w-40

3 - samples will then be taken every three months - use factors noted in %, and top ups noted as is normal

4 - oil will be changed @ 20 000 kms ( maximum Porsche recommended ) or as the samples determine - whichever is first

5 - results will be posted here if anybody is interested

Note 1: Analysis will cover contamination, wear metals and viscosity - a "normal" analysis

Note 2: As we do NOT have a wear metal "history" on this engine the most meaningful parts will probably be related to contamination and viscosity

Note 3 : This engine has been well serviced from new and the speedo reads 109000 kms at present
Please comment

Regards
__________________
Doug Hillary
Rennlist Member # 030204-2681/060810-4400
01 Boxster (986) 2.7 Tiptronic
06 Mercedes Benz CLK Kompressor
(MY89 928S4 Auto - sadly sold)


03-05-2003, 02:58 AM
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


04-30-2003, 07:34 PM
This then is the second report, six months after the oil and filter were changed

Details:
Car - MY89 928S4
Speedo - 111831kms
Oil - Shell Helix Ultra 15w-50 - full synthetic
Oil/filter change date - 10/17/02
Distance since - 8316kms
Oil used - nil
Date of this sample - 4/21/03
Distance since last sample - 1719kms
Use in period - 17% town,31% urban,52% hiway
Avg speed in period - 66 km/h
Fuel economy in period - 12.3ltr-100km
Ambient in period - 34c high to 21c low
Humidity in period - 98% highest</font></li>
Oil Condition - "use" factors;

· Note - last report figures shown thus new/old
Viscosity - 98/94 OK
Water - 0.01%/0.00% OK
Soot Index - 0.00/0.01 OK
TAN - 2.6/3.2 OK - the Max allowed is 8.9

Lab. Report Summary

ExxonMobil's rating - "O-Normal"
Status-Excellent for continued use
Last Report - "O-Normal"
Estimate of distance to oil change - 25000kms
Estimate of total oil life distance - 34000kms

Elemental Analysis;
Iron - 7/6
Aluminium - 2/3
Chromium - &lt;1/1
Copper - 5/3
Lead - 4/4
Silicon - 11/22
Sodium - 2/5

· Note: None of the movements are significant. The silicon level fall is positive
The oil has survived 8316kms (5100lms) and six months very well. Porsche's recommendations look good
Regards

07-17-2003, 07:39 PM
This is the third report on the oil in my car - at nine ( 9) months.
The testing was commenced six months ago to confirm the oil change recommendations from Porsche namely - 20000kms or 12 months for "normal" use
This sample was taken nine months after the oil and filter were changed

Details:

Car - MY89 - 928S4 Auto
Speedo - 114848kms
Oil - Shell Helix Ultra 15w-50 - SJ/CF, A3-96/B3-96 - fully synthetic
Oil/filter change date - 10/17/02
Distance since Oil/filter changed - 11333kms
Oil used since fill - nil
Date of this sample - 7/14/03
Distance since last sample - 3017kms
Use in period - 15% town,25% urban,60% hiway
Avg speed in period - 69 km/h
Fuel economy in period - 11.8ltr-100km
Ambient in period - 26c high to 4c low
Humidity in period - 98% highest
OIl Condition - "use" factors;

Note - last report figures below are shown thus: newest-last-oldest

Viscosity - OK - 98-98-94 ( excellent )
Water - OK - 0.05%-0.01%-0.00% ( excellent )
Soot Index - OK - 0.00-0.00-0.01 ( excellent )
TAN - OK - 4.6-2.6-3.2 ( very good ) the Max allowed is 8.9

Lab. Report Summary

ExxonMobil's rating - "Normal"
Status-Excellent for continued use
Last Report - "Normal"
Estimate of distance remaining to oil change - 3700kms ( 2300 miles ) 3 months
Estimate of distance of oil life left to change - 15000kms ( 9500 miles )
Estimate of total distance to end of oil life - 27000kms ( 16700 miles )

Elemental Analysis;

Iron - 9-7-6 ( excellent )
Aluminium - 3-2-3 ( excellent )
Chromium - 1-<1-1 ( excellent )
Copper - 8-5-3 ( very good )
Lead - 7-4-4 ( very good )
Silicon - 5-11-22 ( excellent )
Sodium - 2-2-5 ( excellent )

Note: None of the elemental movements are significant

The oil has survived for 11333kms (7038 miles) and nine months very well. Porsche's recommendations are looking very very good and with a big margin too!!
Regards


10-09-2003, 07:50 AM
This is the fourth and the final Oil Condition Report concerning the oil in my car - at approx. twelve (12) months and at the oil change point

The Used Oil Analysis ( UOA ) commenced nine months ago - the oil had been in the engine three months then. It was undertaken to confirm Porsche's original oil change recommendations for the 928 - namely, 20000kms or 12 months for "normal" use
The engine oil is now at the maximum time limit set by Porsche, not the distance limit
Used Oil Analysis is used by Equipment Manufacturers, Fleet Managers and Race Teams worldwide. The standardised testing processes compare the original ( virgin ) oil's composition alongside the used oil sample. I have been involved with this process since the late 1960's

The oil and filter were changed at this sampling point even though the ExxonMobil report OK'd the oil for continued use

It was my call to change it out now as it follows Porsche's prescribed maximum time limit

Details:

Car - MY89 - 928S4 Auto
Speedo - 117084kms ( 72709 miles)
Oil - Shell Helix Ultra full synthetic 15w-50 - SJ/CF**, A3-96/B3-96
Oil/filter change date - 10/17/02
Distance since Oil/filter changed - 13569kms (8426 miles)
Oil used since fill - nil ( level only 200ml down = total volume of all samples )
Date of this sample - 10/07/03
Distance since last sample - 2236kms (1388miles)
Use in this period - 16% town,40% urban,44% hiway
Avg speed in this period - 71 km/h ( 44mph)
Fuel economy in this period - 11.7ltr-100km (24 mpg Imp) ( 20 mpg US )
Ambient in this period - 28c high to -2c low
Ambient - annual historical averages - 27.5c max. & 21.5c min.
Ambient - actual in 12 months - max. 40c & min. -2.5c
Humidity in this period - 96% highest
** This oil has a later "rating" than in the 928 S4's Handbook - technology has moved on since 1989. It is not the very latest API oil rating - SL/CF ( and A3/B3 ) - which should perform even better than this oil did over the time and/or distance limits!

Oil Condition - "use" factors;

Note - report figures below are shown thus: now-3-2-1(1=first sample)

Viscosity OK - 98-98-98-94 ( excellent )
Water OK - 0.06%-0.05%-0.01%-0.00%
Soot Index OK - 0.00-0.00-0.00-0.01
TAN OK - 3.8-4.6-2.6-3.2 ( excellent ) the Max allowed is 8.9

Lab. Report Summary

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

Estimated oil's lifespan left until change required - 24500kms ( 15200 miles )
Estimated total of oil's lifespan - 38000kms ( 23500 miles )

Elemental ( & wear metal ) Analysis;

Industry "acceptable" rates (range rounded) - not 928 specific - shown as ((?))
My engine's averages are shown as [?]

Iron 10-9-7-6 ( excellent ) ((30-100)) [ 8 ]
Aluminium 4-3-2-3 ( excellent ) ((5-30)) [ 3 ]
Chromium 1-1-<1-1 ( excellent ) ((1-30)) [ 1 ]
Copper 4-8-5-3 ( excellent ) ((10-30)) [ 5 ]
Lead 7-7-4-4 ( excellent ) ((40-100)) [ 5.5 ]
Silicon 5-5-11-22 ( excellent ) ((10-30)) [ 10.75 ]
Sodium 6-2-2-5 ( excellent ) ((8-10)) [ 3.75 ]

Note:

None of the elemental "movements" have ever been significant. All are at or well below Industry acceptable figures. This indicates that rings, pistons, bores, cams, bearings and other major components are wearing at a very low rate

Oil Condition Summary:

The oil itself has survived for 13569kms ( nearly 8500 miles) and nearly twelve (12) months very very well. The oil's degradation has been very low and its ability to fight acidic corrosion is better than many new cheaper oils. It's viscosity has remained exceptionally close to the original new "virgin" oil - virtually no thicker or thinner than at the start 12 months ago
On the oil's condition readings alone, it could have been left in for another extended period of use. This is but one advantage of a good quality synthetic lubricant

UOA Test Results Summary:

Porsche's Handbook recommendations for normal use are hereby confirmed by the UOA and with a big margin too!! Newer specification oils either mineral or synthetic, will extend the margin still further
Like everything else, time has "moved on" and so has the quality of the oils we can readily purchase today. There has been about five quality upgrades since 1989 alone!!

As a result of the UOAs, the engine has now been put on to Mobil's Delvac 1 5w-40, a lighter viscosity Heavy Duty commercial diesel oil. This oil is the very latest rated diesel oil - API CI/SL - it also exceeds ACEA's A3 and B3 ( E3,4,5 & B4) and is suitable for high performance petrol engine vehicles too. It will stay on this oil as I have good access to this product - it is also used in my heavy and light trucks - and in my other cars too

It will be argued by some ( and indeed already has been here ) that my car gets an "easy life" - I accept that I am probably rated as a smooth and sensible Driver. I was in volved Prototype Vehicle Development including Test Driving many years ago and by experience/knowledge do not abuse my vehicles - but I always know their limits!
I would say that my car is treated close to the way the average 928 owner treats their vehicle.

According to our "Landsharkoz" information, the ownership profile of the 928 is 95% male and aged in the 45-50 range. 57% are self employed and own two or three other cars.
I'm about an "average" owner/user then, just a bit older and I own more cars! And I drive about 40000 miles per annum

I hope this is of interest

George D

Now that is a great post. Thanks for sharing very good data.

ausgeflippt951

Wow what an interesting post. Can anyone contact Exxon/Mobil and have their oil periodically analyzed?

Frumkin

Answered my questions. Thanks for the great post. as a pilot we use oil analysis as a bible. Great!

gruhsy

Yes

Chris White

I feel that the best oil change schedule is to change the oil every time you replace the head gasket....

If you want to try a very good race oil look up Millers oil (sold by Racers Edge). Not cheap...not even vaguely close to cheap....but good. Karl ran a full season in his stock class 911 without changing the oil. Numerous analysis performed - its all documented. If you can run a full season of hard racing (Karl has many track records) on the same oil in a 911 then it passes a serious real world test in my book!

333pg333

Don't think this thread was aimed at that sort of application Chris.

ehall

Wait! yes it is, EXACTLY! This was about the quality of a synthetic oil. That's a pretty damned awesome, real world test of a specific oil. That was one oil through a hard race season, with NO CHANGES! The other, with all the data was really good too, but what Chris posted was pretty freakin strong. Just my opinion, of course.


I didn't bring that around well. If that oil can deliver that performance, under those conditions, it is very much something that the O.P. should consider for a street car.