Oil and Oil...

[oilman]

The problem with 5w-50 is the "wide viscosity" range it covers which makes it almost impossible to make it "shear stable".

You see to meet 5w and sae 50, it needs bucket loads of VI Improver in it to prop it up which makes it prone to shearing at high temperatures that's why 5w-40 and 10w-50 are better options.

As I have mentioned before, the oil would be an sae 50 on day one but would shear back with use (a couple of thousand miles) to an sae 40 or 30.

A shear stable 40 would give better long term protection.

Here is the science:

VI improvers are polymers that expand and contract with changes in temperature. At low temperatures they are very compact and affect the viscosity of a lubricant very little. But, at high temperatures these polymers "expand" into much larger long-chain polymers which significantly increase the viscosity of their host lubricant.

So, as the basestock loses viscosity with increases in temperature, VI improvers "fight back" against the viscosity drop by increasing their size. The higher the molecular weight of the polymers used, the better the power of "thickening" within the lubricant. Unfortunately, an increase in molecular weight also leads to an inherent instability of the polymers themselves. They become much more prone to shearing within an engine.

As these polymers are sheared back to lower molecular weight molecules, their effectiveness as a VI improver decreases. Unfortunately, because petroleum basestocks are so prone to viscosity loss at high temperatures, high molecular weight polymers must be used. Since these polymers are more prone to shearing than lower molecular weight polymers, petroleum oils tend to shear back very quickly. In other words, they lose their ability to maintain their viscosity at high temperatures

Cheers
Simon

 

[944Turbo]

The small oil leaks are what put me off the 0 oils, they are thinner when cold so I assume run out faster, oil isn't any good for the engine if its on the driveway.

Tony

 

[944Turbo]

the other thread has a table showing the reccomended oil viscosities for my car taken from the handbook I guess an S2 would be similar or the same, oil thread
Tony

 

[Diver944]

ORIGINAL: lali

Best Engine Oil ?
And Gearbox Oil?

Lali

So Lali.........have you decided what to use yet? [][][]

 

[TTM]

ORIGINAL: oilman

The problem with 5w-50 is the "wide viscosity" range it covers which makes it almost impossible to make it "shear stable".

Just to add a bit to this thread.
A buddy has done a (little) study some months ago at his work. Report available here.
The Castrol RS does not "shear away" too much, by the way, though it was 10W50, not 10W60.

 

[oilman]

ORIGINAL: 944Turbo

the other thread has a table showing the reccomended oil viscosities for my car taken from the handbook I guess an S2 would be similar or the same, oil thread
Tony

You will find that 5w-40 in the handbook covers the widest viscosity range and therefore if the best for "all year round" use.

My database says 5w-40 or 10w-40 is recommended and this does add up.

The trick is to use a "shear stable" 5w-40 which will give the "year round" useage but also more protection when using the car hard as it will have good thermal stability.

I'm sure that 0w oils did not exist outside of "motorsport" when your car was made. A modern day 944 would read something like 0w-30 or 5w-40 if there was such a thing.

Cheers
Simon

 

[oilman]

ORIGINAL: TTM

ORIGINAL: oilman

The problem with 5w-50 is the "wide viscosity" range it covers which makes it almost impossible to make it "shear stable".

Just to add a bit to this thread.
A buddy has done a (little) study some months ago at his work. Report available here.
The Castrol RS does not "shear away" too much, by the way, though it was 10W50, not 10W60.

Everything is relative, read my posts concerning "true" synthetics and "shear stability", I can assure you that RS 10w-60 is not a true synthetic and I have chemical analysis to back this up. To be honest (and I sell it, so need to be careful here) it's not special.

You cannot cover such a wide viscosity range with a "petroleum" based oil without buckets of VI Improver and that's where the weakness occurs.

It will be outperformed in terms of superior protection everytime by a "shear stable" true synthetic (Ester/PAO) 5w-40 or 10w-50 fact.

There is no comparison between the real thing and modified mineral oils.

The problem as I've mentioned before is the branding of inferior oils "synthetic" due to the US Court Decision when they are not. For a start, they are not built in laboratories "brick by brick" by chemists.

Cheers
Simon

 

[TTM]

Edited by Paul: Thom I have reinstated this post from the recycle bin then deleted all the text (as it's nearly the same as your next post)

There is a bug whereby I cannot see any posts after a recycled one [&:] hence why I have re-instated it []

 

[Guest]

So i assume the Mobile 1 0W-40 is shear stable then? is that the widest range?

Is RS 0W-40 fully synthetic?

 

[TTM]

oilman - I perfectly understand what you say, and I don't mean you're wrong in any way as I'm no oil expert at all.

However my only point here is that the non-synthetic oil Castrol 10W60 has so far proved to be an excellent oil for 944s, although it is written in the owner's manual to put 100% synthetic oil ONLY in 944 engines to avoid bore damages and although it is not as "shear stable" as some other types of oil.
I do believe that whatever the level of theory required to reckon it's not as good as other types of oil and whatever Porsche say, it is what actually happens and what is observed in 944 engines that matters.
I have looked at various dismantled 944 turbo and NA engines. Those using Mobil 1 had scored cylinder walls, those using Castrol had not. I guess the scoring being exclusively related to the type of oil would be difficult if not impossible to prove, however it's proved enough for several friends and me to justify swichting to Castrol 10W60.

Cheers.

 

[Kevin Welch]

Simon

Have you got any info / comments about Valvolene Syn Power full synthetic 5w 40 as Ive just done an oil change using this and am now wondering if I should start worrying.

 

[oilman]

ORIGINAL: slim_boy_fat

So i assume the Mobile 1 0W-40 is shear stable then? is that the widest range?

Is RS 0W-40 fully synthetic?

Yes, both of these need to be PAO or Ester (PAO as it happens) to meet the 0w test at -35 degC and the sae 40

They should be shear stable as the base is synthetic not petroleum therefore little or no VI Improver required.

Cheers
Simon

 

[oilman]

ORIGINAL: Kevin Welch

Simon

Have you got any info / comments about Valvolene Syn Power full synthetic 5w 40 as Ive just done an oil change using this and am now wondering if I should start worrying.

It's difficult to comment on many individual oils as the tests that we have, and we have many may not relate the specific product but judging by the ones that we have, it's likely to be a molecularly modified or hydrocracked oil, no ester or pao used.

I don't think you need to worry but shall we say you could have bought much better for your "pride and joy".

Cheers
Simon

 

[Kevin Welch]

ORIGINAL: oilman

ORIGINAL: Kevin Welch

Simon

Have you got any info / comments about Valvolene Syn Power full synthetic 5w 40 as Ive just done an oil change using this and am now wondering if I should start worrying.

It's difficult to comment on many individual oils as the tests that we have, and we have many may not relate the specific product but judging by the ones that we have, it's likely to be a molecularly modified or hydrocracked oil, no ester or pao used.

I don't think you need to worry but shall we say you could have bought much better for your "pride and joy".

Cheers
Simon

Many Thanks Simon

It looks like it might be a short interval oil change this time around.[]

 

[oilman]

ORIGINAL: Chris Goodman

Simon

What would you recommend for 944 Turbo SE, used for road and a number of track days? I noticed that with Mobil 1 oil pressure dropped to about 3 bar during recent trackdays at Dijon & Magny Cours (where ambient temp was 25-ish degrees). Brakes became 'spongy' with Dot 5.1 and I'm having braided hoses fitted as we speak - in case that's the prob rather than fluid??

Chris

Chris,

Sorry but I missed this one.

The recommendation is for 5w-40 or 10w-40.

I would suggest (due to the trackdays) that you look at a "shear stable" 5w-40 as the first option as this will operate between 90-110 degC with the ability to cope for prolonged periods at 130 degC.

The 5w will also give you good cold start protection.

10w-50 can be considered but you will sacrifice some cold start protection for normal winter driving.

You can always email me for a price list.

Cheers
Simon

 

[lali]

Ive got some swepco gear oil ready to go in and i picked up some 15-40 magnatec from Halfords yesterday. All I need now is to book it in and Im sorted... ish...

 

[TTM]

Just thought I'd mention that I was confirmed this week-end by a honourable German gentleman who worked at Porsche, who is co-founder of TTP (820 Boxster twin turbo conversions sold world wide, so far) and owner of TTT that the Castrol RS 10W60 is the only oil that may be used in 944-type cars, as in these days the engines were not designed to work with 0W-- or 5W--.

Cheers.

 

[944Turbo]

Castrol RS the only oil? or only 10w40, 10w50, 20w50 ( I hate Castrol oil or more correclty my tuned Minis hated it, though admitedly not RS)

Oh and I ordered some Silkoline from Simon - it arrived next day. Not put it in the car yet but the delivery service was good.

This image taken from the handbook ( but lightly modified) would seem to indicate 5w oils were available at least by 1990.

Tony

 

[944Turbo]

PS on rennlist they have just started a debate on which oil is best - I kept out of it! and on which tyres are best saying Kumho's are rubbish the reverse of what recent experience would indicate hear - but the compound may be different I suppose.


On Oil I have had well respected 944 maintenance specialists,
Reccomend Texaco / Shell semi synthetic.
Castrol 'special oil' for older engines (not a synthetic).
Mobil one motorsport which I had also concluded was the best.
I have heard a diferent oil specialist recommend castrol magnatec (but iirc he worked for castrol)

Generally everywhere I hear turbos should have a good synthetic due to the heat

On forums I have heard 'our engines were designed before synthetics so they shouldnt be used, they will leak out as they are runnier and will destroy the seals etc. All of which I neglect as in my experience it is untrue.

Recently Simon has ben putting forward lots of info that makes sense, enough for me to give the silkoline a try (and he sells other oils including mobil 1 though I still wonder which one gives the biggest profit margin [] - I am such a cynic! )

Andrew sells Royal Purple which I was also considering trying, but It is relatively new to the UK market (and I am a conservative cycnic) it also seems to be more expensive than mobil 1 here, my previously trusted oil.

So thats my random views on oil,
Tony

 

[oilman]

I'm sorry but 10w-60 is too thick and can cause problems, I would not use an thicker than 10w-50.

Surely the thicker the oil the better!

This isn't always true - even when using a petroleum oil.

Although it is true that heavier viscosity oils (which are generally thought of as being thicker) will hold up better under heavy loads and high temperatures, this doesn't necessarily make them a better choice for all applications.

On many newer vehicles only 0w-40, 5w40 or 10w40 engine oils are recommended by the
manufacturer. If you choose to use a higher viscosity oil than what is recommended, at the very least you are likely to reduce performance of the engine. Fuel economy will likely go down and engine performance will drop.

In the winter months it is highly recommended that you not use a heavier grade oil than what is recommended by the manufacturer. In cold start conditions you could very well be causing more engine wear than when using a lighter viscosity oil. In the summer months, going to a heavier grade is less of an issue, but there are still some things to be aware of.

Moving one grade up from the recommended viscosity is not likely to cause any problems (say from a 10w40 to a 10w50 oil). The differences in pumping and flow resitance will be slight. Although, efficiency of the engine will decrease, the oil will likely still flow adequately through the engine to maintain proper protection. However, it will not likely protect any better than the lighter weight oil recommended by the manufacturer.

Moving two grades up from the recommended viscosity (say 10w40 to 10w-60) is a little more extreme and could cause long term engine damage if not short term. Although the oil will still probably flow ok through the engine, it is a heavier visocosity oil. As such it will be more difficult to pump the oil through the engine. More friction will be present than with a lighter viscosity oil. More friction will be present than with a lighter viscosity oil. More friction means more heat. In other words, by going to a thicker oil in the summer months, you may actually be causing more heat build-up within the engine. You'll still be providing adequate protection from metal to metal contact in the engine by going with a high viscosity, but the higher viscosity will raise engine temperatures.

In the short run, this is no big deal. However, over the long term, when engine components are run at higher temperatures, they WILL wear out more quickly. As such, if you intend on keeping the vehicle for awhile, keep this in mind if you're considering using a heavier weight oil than the manufacturer recommends.

The best advice is to is to stay away from viscosity grades that are not mentioned in your owner's manual.

I believe that this is good advice and that moving to too heavier oil is just as bad as using an oil that's too light.

Cheers
Simon