Which Oil for S2?
- Thread starter LOZ944
- Start date
When I get home I'll post our manual. It shows Oil recommendations / temp ranges for Mineral and Synth.
I think we tend to focus on fuel consumption too much when selecting oil. A very big part of what the oil is there for is to protect vulnerable metal parts in a suspensive manner. As the oil gets thinner with heat and load, such as on the track, you need it to remain as much in it's original form. Same with cold start. If you have a lightweight oil it will drop down out of the cam tower and increase wear. Especially if you don't use it regularly.
There was a massive increase in engine wear for some time when many people switched to M1. What lent more weight to this theory was when the wear factor returned to normal (virtually nil) when many of the local workshops went back to a Multi Grade mineral oil with decent viscosity and ZDDP content.
Many thanks to you all for your advice, very much appreciated. I would say though
I'm probably no wiser as there seems to be a definetive divide between mineral,
semi synthetic and synthetic users! I think I'll look at it less subjectively and take
Sawood12 and Diver944 advice, quotes such as: "˜every car is different as it ages
and what might suit one will not be right for another,' and
"˜My advice is best not to get too hung up on oil.'
This is not to say I won't take others advice into account but I thank you all for
your valuable expertise.
All the best and happy motoring.
I'm probably no wiser as there seems to be a definetive divide between mineral,
semi synthetic and synthetic users! I think I'll look at it less subjectively and take
Sawood12 and Diver944 advice, quotes such as: "˜every car is different as it ages
and what might suit one will not be right for another,' and
"˜My advice is best not to get too hung up on oil.'
This is not to say I won't take others advice into account but I thank you all for
your valuable expertise.
All the best and happy motoring.
Sandspider
New member
Just thought I'd add my tuppence worth -
I used to run my car on 10W40 semi synth, and all was fine (very low oil consumption indeed, maybe 0.5l per 5000 miles). At most recent chance I put in 5W40 fully synth, and oil consumption increased dramatically. (Don't have a figure to hand as car is currently off the road :-(, but more like 1l per 750 miles).
I wouldn't have thought the minor change in grade (only applies when engine is cold after all) would have made such a difference, so I'm assuming it's because the fully synth stuff is thinner than the semi synth. (The excess oil isn't burning in my exhaust, and isn't leaking on to my drive, so I can only assume it's leaking out somewhere under acceleration and falling on to the road while I'm in motion...)
HTH
Giles
I used to run my car on 10W40 semi synth, and all was fine (very low oil consumption indeed, maybe 0.5l per 5000 miles). At most recent chance I put in 5W40 fully synth, and oil consumption increased dramatically. (Don't have a figure to hand as car is currently off the road :-(, but more like 1l per 750 miles).
I wouldn't have thought the minor change in grade (only applies when engine is cold after all) would have made such a difference, so I'm assuming it's because the fully synth stuff is thinner than the semi synth. (The excess oil isn't burning in my exhaust, and isn't leaking on to my drive, so I can only assume it's leaking out somewhere under acceleration and falling on to the road while I'm in motion...)
HTH
Giles
oilman
New member
Putting all of the arguments aside, lets look at the facts as 0w and 5w are not too thin.
0w-40, 5w-40, 10w-40 and 15w-40 are all the same thickness (14cst) at 100degC.
Centistokes (cst) is the measure of a fluid's resistance to flow (viscosity). It is calculated in terms of the time required for a standard quantity of fluid at a certain temperature to flow through a standard orifice. The higher the value, the more viscous the fluid.
As viscosity varies with temperature, the value is meaningless unless accompanied by the temperature at which it is measured. In the case of oils, viscosity is generally reported in centistokes (cst) and usually measured at 40degC and 100degC.
So, all oils that end in 40 (sae 40) are around 14cst thickness at 100degC.
This applies to all oils that end in the same number, all oils that end in 50 (sae 50) are around 18.5cst at 100degC and all oils that end in 60 (sae 60) are around 24cst at 100degC.
Now, ALL oils are thicker when cold. Confused? It's true and here is a table to illustrate this.
Grade..............0degC.................................10degC................................40degC.................................100degC
0w-20...............329......................................181......................................46...................................... ..9cst
0w-30...............540......................................290......................................68........................................12cst
5w-30...............654..................................... 338..................................... 74........................................12cst
0w-40...............665..................................... 354......................................82........................................14cst
5w-40...............874..................................... 440..................................... 91........................................14cst
10w-40.............842 .....................................430......................................91....................................... 14cst
15w-40.............1260....................................595.....................................107.......................................14cst
5w-50...............888......................................474.....................................109.......................................18cst
10w-50.............1034....................................537.....................................116.......................................18cst
15w-50.............1535....................................735.....................................135.......................................18cst
20w-50............ 2300....................................1013...................................157.......................................18cst
10w-60.............1553.....................................795....................................165.......................................24cst
20w-60............. 2390....................................1123..................................195.......................................24cst
As you will see, there is penty of viscosity at 0degC and 10degC, in fact many times more than at 100degC and this is the problem especially in cold weather, the oil must flow quick enough to protect vital engine parts at start up and the lower the "w" number, the faster the flow when cold!
So, given that an sae 40 is 14cst at 100degC which is adequate viscosity to protect your engine (and is the primary handbook recommendation), and much thicker when cold, how can a 5w or 0w oil be too thin?
Well, it can't is the truth.
You see, the clever part (thanks to synthetics) is that thin base oils can be used so that start up viscosity (on say a 5w-40 at 0degC) is reduced to around 800cst and this obviously gives much better flow than an old fashioned monograde sae 40 which would have been around 2579cst at 0degC although still 14cst at 100degC.
So, how does this happen, well as explained at the beginning, it's all about temperature, yes a thin base oil is still thicker when cold than at 100degC but the clever stuff (due to synthetics again) is that the chemists are able to build these oils out of molecules that do not thin to less than 14cst at 100degC! So, there you have it, not say so................just facts.
I would always recommend using better quality synthetic oils of around a 5w-40 grade in your cars as it makes perfect sense and is a better choice long term than an inferior mineral or semi-synthetic. Profit margins do not come into it, we sell less litres of synthetic as it needs changing less frequently and yet make the same profit margin!
Cheers
Simon
0w-40, 5w-40, 10w-40 and 15w-40 are all the same thickness (14cst) at 100degC.
Centistokes (cst) is the measure of a fluid's resistance to flow (viscosity). It is calculated in terms of the time required for a standard quantity of fluid at a certain temperature to flow through a standard orifice. The higher the value, the more viscous the fluid.
As viscosity varies with temperature, the value is meaningless unless accompanied by the temperature at which it is measured. In the case of oils, viscosity is generally reported in centistokes (cst) and usually measured at 40degC and 100degC.
So, all oils that end in 40 (sae 40) are around 14cst thickness at 100degC.
This applies to all oils that end in the same number, all oils that end in 50 (sae 50) are around 18.5cst at 100degC and all oils that end in 60 (sae 60) are around 24cst at 100degC.
Now, ALL oils are thicker when cold. Confused? It's true and here is a table to illustrate this.
Grade..............0degC.................................10degC................................40degC.................................100degC
0w-20...............329......................................181......................................46...................................... ..9cst
0w-30...............540......................................290......................................68........................................12cst
5w-30...............654..................................... 338..................................... 74........................................12cst
0w-40...............665..................................... 354......................................82........................................14cst
5w-40...............874..................................... 440..................................... 91........................................14cst
10w-40.............842 .....................................430......................................91....................................... 14cst
15w-40.............1260....................................595.....................................107.......................................14cst
5w-50...............888......................................474.....................................109.......................................18cst
10w-50.............1034....................................537.....................................116.......................................18cst
15w-50.............1535....................................735.....................................135.......................................18cst
20w-50............ 2300....................................1013...................................157.......................................18cst
10w-60.............1553.....................................795....................................165.......................................24cst
20w-60............. 2390....................................1123..................................195.......................................24cst
As you will see, there is penty of viscosity at 0degC and 10degC, in fact many times more than at 100degC and this is the problem especially in cold weather, the oil must flow quick enough to protect vital engine parts at start up and the lower the "w" number, the faster the flow when cold!
So, given that an sae 40 is 14cst at 100degC which is adequate viscosity to protect your engine (and is the primary handbook recommendation), and much thicker when cold, how can a 5w or 0w oil be too thin?
Well, it can't is the truth.
You see, the clever part (thanks to synthetics) is that thin base oils can be used so that start up viscosity (on say a 5w-40 at 0degC) is reduced to around 800cst and this obviously gives much better flow than an old fashioned monograde sae 40 which would have been around 2579cst at 0degC although still 14cst at 100degC.
So, how does this happen, well as explained at the beginning, it's all about temperature, yes a thin base oil is still thicker when cold than at 100degC but the clever stuff (due to synthetics again) is that the chemists are able to build these oils out of molecules that do not thin to less than 14cst at 100degC! So, there you have it, not say so................just facts.
I would always recommend using better quality synthetic oils of around a 5w-40 grade in your cars as it makes perfect sense and is a better choice long term than an inferior mineral or semi-synthetic. Profit margins do not come into it, we sell less litres of synthetic as it needs changing less frequently and yet make the same profit margin!
Cheers
Simon
edh
New member
It's a very odd field - or seems to be
I've found that castrol edge 10w60 disappeared from my engine at a rate of knots! - millers CFS 10w60 doesn't. I've also discovered that the oil pressure gauge in my turbo isn't entirely accurate - my oil pressure shows a drop as I get hard on the boost, which appears to be an electrical problem. I have a second gauge now that works just fine.
I've fitted some more cooling (track temps were approaching 130C) and will see how we get on with Silkolene 15w50 synth (I think that's right - it was from those nice people at Opie so it will be great [
])
I've found that castrol edge 10w60 disappeared from my engine at a rate of knots! - millers CFS 10w60 doesn't. I've also discovered that the oil pressure gauge in my turbo isn't entirely accurate - my oil pressure shows a drop as I get hard on the boost, which appears to be an electrical problem. I have a second gauge now that works just fine.
I've fitted some more cooling (track temps were approaching 130C) and will see how we get on with Silkolene 15w50 synth (I think that's right - it was from those nice people at Opie so it will be great [
])To extrapolate the table shown above, even at 100degrees the 20w/60 has a huge advantage cst over the low visc synths. So what happens at 130degrees on the track? You've got a bit of thin hot water protecting your bearings under huge load and g forces.
Interesting to note that the factory still recommends a 20w/50 mineral in 987 and 996 engines down to below freezing? Still the inherent design faults of those engines won't be saved even by good oil. []
Why, if the M1 synthetic and the like is so good, was there a huge rate of engine wear when workshops changed to these oils, and when they changed back it disappeared? Why is it when almost all engine failures on our cars around the world are using low visc, synth oils? To qualify, the failures and issues are largely when cars are on the track. If you're just going to pootle around on the street hitting boost for 2-4 seconds at a time, then it probably won't matter nearly as much. You will still have certain component engine wear if the oil has seeped down into the crankcase overnight, but not total failures as such.
Interesting to note that the factory still recommends a 20w/50 mineral in 987 and 996 engines down to below freezing? Still the inherent design faults of those engines won't be saved even by good oil. [
]Why, if the M1 synthetic and the like is so good, was there a huge rate of engine wear when workshops changed to these oils, and when they changed back it disappeared? Why is it when almost all engine failures on our cars around the world are using low visc, synth oils? To qualify, the failures and issues are largely when cars are on the track. If you're just going to pootle around on the street hitting boost for 2-4 seconds at a time, then it probably won't matter nearly as much. You will still have certain component engine wear if the oil has seeped down into the crankcase overnight, but not total failures as such.
oilman
New member
I've seen this many times before on many different car forums and for every car that burns more oil there is one that burns little or nothing on the same oil or viscosity. It can be down to a number of factors. Oil quality/basestocks, type of use, past life, mileage, historical wear etc.
If you had a poll and most owners voted then you would see that your views here with regards to synthetics and oil burning are represented by a small few. We have a huge number of Customers using light viscosity oils in 80's engines without issues, sure some burn more than others but that's unavoidable.
Cheers
Simom
If you had a poll and most owners voted then you would see that your views here with regards to synthetics and oil burning are represented by a small few. We have a huge number of Customers using light viscosity oils in 80's engines without issues, sure some burn more than others but that's unavoidable.
Cheers
Simom
oilman
New member
The oils pressure dropped from using what?
I would expect the oil pressure to drop from a 10w-60 toa 5w-40 but changing quality should not affect it in fact a synthetic will stay in grade longer so oil pressure would be retained over a longer period with less shear-back.
Also bear in mind that although an amount of oil pressure is required in any car, oil pressure = resistance and oil flow is equally important.
If I remember wasn't this the £1k car?
Cheers
Simon
I would expect the oil pressure to drop from a 10w-60 toa 5w-40 but changing quality should not affect it in fact a synthetic will stay in grade longer so oil pressure would be retained over a longer period with less shear-back.
Also bear in mind that although an amount of oil pressure is required in any car, oil pressure = resistance and oil flow is equally important.
If I remember wasn't this the £1k car?
Cheers
Simon
oilman
New member
ORIGINAL: edh
It's a very odd field - or seems to be
I've found that castrol edge 10w60 disappeared from my engine at a rate of knots! - millers CFS 10w60 doesn't. I've also discovered that the oil pressure gauge in my turbo isn't entirely accurate - my oil pressure shows a drop as I get hard on the boost, which appears to be an electrical problem. I have a second gauge now that works just fine.
I've fitted some more cooling (track temps were approaching 130C) and will see how we get on with Silkolene 15w50 synth (I think that's right - it was from those nice people at Opie so it will be great [
This illustrates my point, about the thickest oil money can buy and still dissapearing. Could be a basestock composition thing but see how you get on with ester/pao 15w-50
Cheers
oilman
New member
ORIGINAL: 333pg333
To extrapolate the table shown above, even at 100degrees the 20w/60 has a huge advantage cst over the low visc synths. So what happens at 130degrees on the track? You've got a bit of thin hot water protecting your bearings under huge load and g forces.
Interesting to note that the factory still recommends a 20w/50 mineral in 987 and 996 engines down to below freezing? Still the inherent design faults of those engines won't be saved even by good oil. [
Why, if the M1 synthetic and the like is so good, was there a huge rate of engine wear when workshops changed to these oils, and when they changed back it disappeared? Why is it when almost all engine failures on our cars around the world are using low visc, synth oils? To qualify, the failures and issues are largely when cars are on the track. If you're just going to pootle around on the street hitting boost for 2-4 seconds at a time, then it probably won't matter nearly as much. You will still have certain component engine wear if the oil has seeped down into the crankcase overnight, but not total failures as such.
As you will be aware, in the UK and Europe, Mobil1 is Porche's oil of choice certainly post mid 90's so there must be some science behind this choice. Porsche's list of approved oils is 90% 0w-40 or 5w-40 oils again there is some science behind this.
Ok these are older cars, generally carrying years of wear and abuse. We run a 928 S4 with over 100,000 miles on the clock here at Opie and we have had no problems on Silkolene Pro S 5w-40 whatsoever with regards to oil pressure or any oil issues, it's as sweet as a nut.
At the end of the day, it works for some and not others, we could argue this for a month and get nowhere but the fact still remains that the lower the "w" number, the better the flow from cold and therefore the lower the wear when you turn the key and that's where 90% of all the wear occurs.
Cheers
Simon
Peter Empson
PCGB Member
Thanks for posting on this thread Simon, it's great to have someone with your knowledge here.
I currently use Silkolene Pro S (guess where I buy it from...) in both my cars, the white car uses lots (the rings are shot), the red car uses very little. Oil pressure on both is perfectly fine, with the white car reading lower (but also running hotter). The ProS also seems to remain looking much cleaner than any other oil I've used so far.
I currently use Silkolene Pro S (guess where I buy it from...) in both my cars, the white car uses lots (the rings are shot), the red car uses very little. Oil pressure on both is perfectly fine, with the white car reading lower (but also running hotter). The ProS also seems to remain looking much cleaner than any other oil I've used so far.
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