A sticky ZP motor oil question.

As explained in the general summary towards the end of the reports, the used engine oil was tested for wear metals and engine viscosity at each lab test with positive results for each, over and beyond the factory recommended drainage interval.

Throughout the lab tests, it is clear that the used engine oil maintained suitable viscosity. Could you please explain the method, significance and implications of the additional testing with a tapered bearing viscometer? Like I said, I am not an engineer. Thanks. ;)

 

Suitable viscosity

Suitable viscosity?, What does it mean? How has it been tested?.

The tapered bearing simulator measures the HTHS ( High Shear High temperature ) behavior of an oil.
To learn more about the tapered bearing simulator or viscometer please visit this link:
http://www.savantgroup.com/TBSViscometer.htm

Multigrade ester and PAO oils have good inherent Viscosity Index characteristics.
Although these group IV base oils are pretty stable , they contain oil soluble polymer additives as VI modifiers or improvers.
Under repeated HTHS conditions these polymers can break down loosing the multigrade efficiency of the oil .

 

Viscosity was tested as part of the Used Oil Analysis performed by the lab in these reports with favorable results throughout the interval recommended by Porsche. How it is tested, I don't know, but apparently these analyses follow a standardised procedure?

 

Standards

Standards may change , and must change, a Saybolt viscometer gives reproducible data, and is and standard in the oil industry. A Brookfield viscometer is also an standard instrument used in many industries , however it doesn't mean that both instruments are adequate to measure the high shear stresses found in high performance engines.

In other words , after a long use, at low shear forces the apparent viscosity can meet the initial oil specifications, but at very high shear stress it could show significant differences.

I wouldn't never extend the recommended oil change period.

I'm not a F1 expert but probably the teams forget all about oil life claims and drain it after every race.

 

Of course, but I was referring to street use. Porsche's recommended 10K km interval is conservative enough in that case.

Lots of amateur GT racing teams trust Mobil1 and Porsche recommends it. I don't see why we shouldn't be comfortable using it for the street. :)

 

Mobil 1

Please take a look at the first post of this thread
Exxon has reduced recently ZDDP the antiwear additive.
When the oil fails, ZDDP or zinc diakyldithiophosphate is the last lubication line of defence . Some racing teams have reported engine faliures when using Mobil 1.

 

I understand that, but are you questioning the use of Mobil1 for the street or for track use?

I think the risks you're referring to only come into play in a track application. For street use, Mobil1 oil is probably as good as any. Why then would Porsche continue to equip new cars with it?

 

Street use: OK, as long as you drive often your Porsche "peacefully",who does it?.
Porsche recomendations: Marketing + $$$$$.:[angel]

 

The Porsche engine failures you are referring to are probably all in 996 series cars, so an ester based oil may very well be advisable in that case. However, I think it's safe to say the 996 based engines have shown more instances of RMS in varying levels of severity than oil-related catastrophic engine breakdowns.

On the other hand, I have yet to hear of an oil-related engine failure in a M44/51 or M44/52 engine car like our 951s' other than through plain oil starvation, such as the notorious Nº2 rod bearing during sharp turns on the race track. In the 951 this risk is greatly averted by adding oil pan baffles (the factory did on the M44/52) and keeping the oil level topped off.

As you know, the 951 series cars were actively campaigned with relative success while running on traditional mineral oils and most of those engines are still running today!

 

Regarding the price difference between Mobil1 0w-40 and Motul 300v 5w-40 it is about 3euro/litre. Not too bad considering the engine benefits or/and peace of mind.

 

Oily questions & answers

I agree with you the 951 turbo engine seems to be more durable than a 996 atmosferic engine.

In 1988 I bought at Kotnik a brand new 944 turbo cup .
They recommended me a Motul oil that performed OK. I drained and refilled it every 10 th km ( the color changed from a pale yellow to a brown colour). I agree with GT3 , now one of the best oils for the 951 ( and 996) is the supersyn Motul 300V 5W-40.
I also own a 996 C4 tip , for this car Porsche recommends the Mobil 1 0W-40. After they changed the formulation I'm not very confident on this lube .
According the Excellence magazine the tiptronic 996 models are less prone to RMS problems, I hope so!!!.

 

Some times the streets conditions are extreme, for instance: Los Monegros, 15hrs. August, high speeds and.... my golf gti 16v engine said bye bye, all just after a recent oil change with Mobil 1. Just a coincidence? may be. But that´s my experience and i don´t want repeat it.

 

Los Monegros

I agree, in my own experience , in a hot summer Los Monegros is a dangerous engine killer dessert .

 

Do you really think it was the Mobil1 oil that killed the engine? A Golf GTI breaks down in Los Monegros and now all the race teams using Mobil1 are wrong? No offense, but that sounds like a bit of a stretch to me.

BTW, not all Mobil1 oil is the same for all applications. Porsche now recommends 0W-40 grade in its newer models, but the Porsche AMAG shop that prepped my 951 for delivery in Switzerland advised not to go any lower than the 5W-50 grade for my 1991 M44/52 engine. That was 8 years ago.

 

Teams

I'd like to know the truth.

Teams get money from their sponsors, but what do they really do??

 

I sincerely hope you find it, and when you do, I'll be the first to switch to Silkolene or whatever ester based oil your conclusive evidence leads you to believe is best. Meanwhile, we are only making guesses, yours being much more educated than mine, but guesses just the same.

Regards, and I hope to run into you again soon. This time with your 951, I hope!

 

Vollblut, sincerely appreciate your comments. Thanks. Dont stop. By the way in Belgium every Porsche dealer uses Mobil 1 5W-50 too.
As i said, dont know exactly the true reason of my engine failure but neither which oil racing teams use.

 

To guess or not to guess, that is the question

Well I'm not trying to guess which oil is best I just want to get the best oil without being influenced by propaganda.

These data were posted by Simon in the GB Porsche Club Forum .

Hope this will help to clarify the "oily scene"

*****************************************************
To explain in the best way I can why oils degrade (shear) with use and the easiest way to identify an oil that will "stay in grade" for longer.

Viscosity Index Improvers.

An oils viscosity will decrease as the engine temperature rises. Viscosity Index Improvers are added to reduce this thinning. They are a key additive in the production of multigrade oils.

VI Improvers are heat sensitive long chain, high molecular weight polymers that increase the relative viscosity of the oil at high temperatures. They work like springs,coiled at low temperatures and uncoiling at high temperatures. This makes the molecules larger (at high temps) which increases internal resistance within the thinning oil. They in effect "fight back" against the viscosity loss in the oil.

"Shearing"

The long chain molecules in VI Improvers are prone to "shearing" with use which reduces their ability to prevent the oil from losing viscosity. This "shearing" occurs when shear stress ruptures the long chain molecules and converts them to shorter, lower weight molecules. The shorter, lower weight molecules offer less resistance to flow and their ability to maintain viscosity is reduced.

This shearing not only reduces the viscosity of the oil but can cause piston ring sticking (due to deposits), increased oil consumption and increased engine wear.

Like basestock quality, VI Improvers also vary in quality. The best quality ones are normally found in synthetic oils (Group IV - PAO / Group V - Esters) and it is important to understand that the less of these in the oil the better the oil will stay in grade.

Which oils require more VI Improvers?

There are two scenarios where large amounts of these polymers are required as a rule.
Firstly in "wide viscosity" multigrades. By this I mean that the difference between the lower "W" number and the higher number is large for example 5w-50 (diff 45) and 10w-60 (diff 50) are what is termed as "wide viscosity" oils.
Narrow viscosity oils like 0w-30 (diff 30) or 5w-40 (diff 35) require far less VI Improvers and therefore are less prone to "shearing".

Secondly, mineral and hydrocracked (petroleum synthetic oils) require more VI Improvers than proper PAO/Ester (Group IV or V) synthetic oils as they are less thermally stable to begin with and this is due to the non-uniform molecules in petroleum oils as opposed to the uniformity of synthetics built in laboratories by chemists.

It is a fact that some synthetics require little or no VI Improvers to work as a multigrade due to their superior thermal stability.

How to identify a good "shear stable" oil.

API and ACEA both conduct tests called HTHS (High Temperature/ High Shear) and all oils carrying these specifications are tested and scored.

For all oils, these test results are available however, they are often ommitted from the oils technical data sheet! Oil Companies have a tendency to publish the figures that they want you to see and therefore you often need to dig further or ask for certain information when comparing the performance of various oils.

High-Temperature/High-Shear

This test is a simulation of the shearing effects that would occur within an engine. In fact, it's actually designed to simulate motor oil viscosity in operating crankshaft bearings.

Under high stress conditions where shearing can occur, the VI Improvers (polymers) break down. As they do, the viscosity of the oil decreases. This is what the High Temperature/High Shear test checks for.

The HT/HS test is measured in Centipoise (cP) as the Cold Crank Simulator test is. However, in this case, because you're hoping for the least loss of viscosity with an increase in heat and stress, you want the cP value to remain high.

Each SAE multi-viscosity grade has a specific lower limit for the HT/HS cP value. If a multi-viscosity oil cannot achieve a cP value above that limit, it cannot be classified under that viscosity grade. For instance, according to the SAE specifications, an oil must achieve an HT/HS cP value of 3.7 or higher in order to be classified at the 15w40 viscosity grade.
The thinner the oil the lower the number.

Comparisons of HTHS numbers.

Here for comparison sake are a few numbers that we have compiled from data sheets and requests to the oil companies concerned. These are well known oils and considered to be "quality" synthetics so these comparisons are relevant.

Silkolene PRO S 5w-40
HTHS 4.07

Motul 300V 5w-40
HTHS 4.51

Silkolene PRO S 10w-50
HTHS 5.11

Motul 300V 10w-40
HTHS 4.19

Silkolene PRO R 15w-50
HTHS 5.23

Motul 300V 15w-50
HTHS 5.33

Mobil 1 Motorsport 15w-50
HTHS 5.11

Castrol RS 10w-60
HTHS 3.70

I'm sorry if this is too complicated but making a complicated subject simple is not easy however if I've lost anyone, please feel free to ask questions.

Cheers,
Simon

 

Like I said, I've been using M1 5W-50 since the Swiss OPC filled my 951 with it in December 2000, when it was not available in stores here in Spain and I had to buy it by the case from a distributor in Cornella, called VILLAGRA, so my choice was not influenced by more recent propaganda surrounding the brand, F1 endorsements, etc.

At any rate, I'm attaching a message I received today by Doug Hillary, whose testing and contributions on this subject in the Rennlist forums has been widely recognized.

 

Oil wars

Well you've posted an interesting expert advice. I'll mind it.