PSD diff oil spec
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From: Oman
PSD diff oil spec
Planning to change the diff oil in the next few days but having trouble understanding yet alone finding what oil is suitable. I am aware that some diff oils are more suited for LSD clutch plates and presumably something similar might apply to the PSD system.
First shop I popped into had a Shell Spirax 90 weight oil which I seem to remember is the original spec viscosity wise. The spec was GL-1 but have no clue as to what that implies. Just about all I know is that the higher the number the greater the load bearing capacity.
Thoughts appreciated
First shop I popped into had a Shell Spirax 90 weight oil which I seem to remember is the original spec viscosity wise. The spec was GL-1 but have no clue as to what that implies. Just about all I know is that the higher the number the greater the load bearing capacity.
Thoughts appreciated
Last edited by FredR; Feb 10, 2021 at 03:36 PM.
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GL5 - 75W90 50:50 Redline and Redline LS
If you cannot get Redline, MOTUL 300V 75w90 LS works wonderfully well in my GT3 box, which incidentally was designed with 928 part numer synchros from the factory...
If you cannot get Redline, MOTUL 300V 75w90 LS works wonderfully well in my GT3 box, which incidentally was designed with 928 part numer synchros from the factory...
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From: Oman
Thanks for the input- I have arrived at the GL5 spec - more a question of what I can find albeit I should be able to find something. There is a good chance the Liqui Moly agents may have something- have you any idea if there is any penalty wear wise if I have to go for a non LS variant?
Last oil change on the diff was done at the local agents - no idea what they used. Quite some time since it was changed but not many miles- probably about 30k miles but over 10 years I think.
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Alex,
Thanks for the input- I have arrived at the GL5 spec - more a question of what I can find albeit I should be able to find something. There is a good chance the Liqui Moly agents may have something- have you any idea if there is any penalty wear wise if I have to go for a non LS variant?
Last oil change on the diff was done at the local agents - no idea what they used. Quite some time since it was changed but not many miles- probably about 30k miles but over 10 years I think.
Thanks for the input- I have arrived at the GL5 spec - more a question of what I can find albeit I should be able to find something. There is a good chance the Liqui Moly agents may have something- have you any idea if there is any penalty wear wise if I have to go for a non LS variant?
Last oil change on the diff was done at the local agents - no idea what they used. Quite some time since it was changed but not many miles- probably about 30k miles but over 10 years I think.
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From: Oman
there shouldn't be - unlike a conventional LSD, the PSD is open most of the time, I got the Red Line recommendation from here, and it was more to do with the way the friction discs engaged within the PSD casette. Not about wear... Unless you are doing 11s at every traffic light and you live at Yas Marina, any decent GL5 should be good... LSD suitable is preferable for the sake of the friction discs, but not a killer like on a classic LSD diff
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From: Oman
I will give the local Mobil agents a call after the weekend. I have not had much to do with them since the local main dealer filled my engine with 0W40 after transplanting my S4 motor 16 years ago- lasted about 10 minutes before I told them to take it out. The local Mobil agents refused to get me some Mobil 1 15W50 so I have used Shell Helix 20W50 ever since- just change it more regularly.
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I will give the local Mobil agents a call after the weekend. I have not had much to do with them since the local main dealer filled my engine with 0W40 after transplanting my S4 motor 16 years ago- lasted about 10 minutes before I told them to take it out. The local Mobil agents refused to get me some Mobil 1 15W50 so I have used Shell Helix 20W50 ever since- just change it more regularly.
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From: Oman
Product selection was all down to Porsche, Not the local agents but the regional office up in Dubai. For the Cayenne fleet Porsche stuck with Mobil 1 0W40 . The Cayenne's were going through so much oil Porsche offered free top ups but it was costing them a bomb. Finally they changed to Liqui Moly 5W40 and the oil consumption improved quite noticeably. Stick that stuff in a 928 and I reckon oil consumption would be equivalent to a small hole in the sump!
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I will give the local Mobil agents a call after the weekend. I have not had much to do with them since the local main dealer filled my engine with 0W40 after transplanting my S4 motor 16 years ago- lasted about 10 minutes before I told them to take it out. The local Mobil agents refused to get me some Mobil 1 15W50 so I have used Shell Helix 20W50 ever since- just change it more regularly.
Last edited by Adamant1971; Feb 11, 2021 at 06:51 PM.
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From: Oman
Thanks for the offer- as I understand airfreighting personal items containing oil is verboten and that before the cost of air freight.
I am sure there will be something suitable available here even if I have to prise something from the Porsche dealers! The Liqui Moly agents are well stocked with their products.
The problem here is the DIY market is almost non existent so there is a dearth of aftermarket parts and support shops. In that regard Dubai is much better but Oman closed its land borders with the Emirates due to covid so for the time being at least the prospect of a trip up to Dubai on the new highway is out for the time being. If all else fails I can leave what is currently in the diff as is given mileage wise [30k miles] it should be capable of much more but it has been in the car for about 10 years
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From: Oman
Managed to find some of the Mobil ! 75W90- they did not have the LS variant so purchased 3 litres of the stuff they had - nearly dropped when they told the price [about $25 a litre] but then after arriving back home I checked the UK on the internet - it seems it is a similar price in the UK [with 20% tax].
Thank goodness we only need the stuff once every millenia! What I have in the diff at the moment has not covered much mileage wise- about 25k miles max but it has been in there for quite some time [10 plus years I reckon].. I doubt the stuff degrades with age but...?
Thank goodness we only need the stuff once every millenia! What I have in the diff at the moment has not covered much mileage wise- about 25k miles max but it has been in there for quite some time [10 plus years I reckon].. I doubt the stuff degrades with age but...?
Last edited by FredR; Feb 14, 2021 at 12:27 PM.
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Managed to find some of the Mobil ! 75W90- they did not have the LS variant so purchased 3 litres of the stuff they had - nearly dropped when they told the price [about $25 a litre] but then after arriving back home I checked the UK on the internet - it seems it is a similar price in the UK [with 20% tax].
Thank goodness we only need the stuff once every millenia! What I have in the diff at the moment has not covered much mileage wise- about 25k miles max but it has been in there for quite some time [10 plus years I reckon].. I doubt the stuff degrades with age but...?
Thank goodness we only need the stuff once every millenia! What I have in the diff at the moment has not covered much mileage wise- about 25k miles max but it has been in there for quite some time [10 plus years I reckon].. I doubt the stuff degrades with age but...?
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From: Oman
One assumes you must have used the Porsche recommended oil before migrating to what you currently use. My handbook says it should have a GL5 straight 90 and that was my initial target- no indication of whether it was a mineral oil or a synthetic but I can more or less guarantee it would have been a mineral oil given the 928 timeline.
No mention in the handbook of using LS diff oils but then the S4, GT and GTS models were never equipped with a LSD unit- they were all kitted with the PSD system.
Doubtless you will have a very sound reason for recommending the LS variant. As I am aware the LS variant is there to promote slippage of the clutch plates to stop the things chattering on slow bends. A friend of mine who used to work here has a lovely 87 manual and about 10 years ago was complaining about such chatter- I explained to him that LSD units are infamous for this unpleasant characteristic and that was probably the issue. As I understand the PSD unit does not require such because once it decides it is "showtime" the response is virtually instantaneous- the control algorithm decides how much lock up is needed and off you go.
Whether or not there is some other additional benefit for having the LS variant I have no idea.