I recall seeing Billman state several times that Mobil 1 75w 90 synthetic has been trouble free in all the years he has been working with the S.

Meets the requirements and has a good track record. That is why I use it.

 

Here are the related pages from the workshop manual. It has "Clutch discs" and it relies on friction.

 

It relies on friction yes but not necessarily friction caused purely by the fluid like a viscous unit does and there is no mention of "clutch discs" in that manual.

 

The hypoid gears chew-up the oil.
When you start with a thinner oil it quickly ends up being thin enough to change the locking bias of the Torsen LSD.
IOW: because it works.

 

@ Rolan Thunder. Clutch disc, Friction Disc, Washer, how ever you call them, they are there. And to me they are very similar in form and function to a motorcycle clutch.
And in a motorcycle, the type of oil used could make a huge difference. Use the wrong oil and the clutch slips....

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@ All: So, i am still puzzled what a difference a LS gear oil could make and if it is safe to use it in the S2000 Differential?
It is mentioned here in the thread that sometiems the tabs of the clutch or friction discs are sheared off and come out the next fluid change.
Could this be caused by using a LS Diff fluid, creating to much friction on the clutch or friction disc and cause them to shear off?

 

Yes it is absolutely fine to use an LS diff oil in a diff that doesn't require it, the only real difference is friction modifier. I doubt you would notice any difference in the way the diff behaves if I am honest.

Cheers,

Guy

 

Thanks for the explanation, I know it will work just fine. I was just wondering what the mentality behind it is here. Based on that logic (you could apply it to the engine as well) surely it would be better to change the diff oil more frequently and use the recommended viscosity? I doubt the thinning down of an SAE90 in the diff is as much as the difference in viscosity using an SAE140 as some are on here, over an SAE90. The temp the oil gets to in the diff will also have an affect on the viscosity of the oil, again potentially affecting the behaviour of the diff.

Cheers,

Guy

 

Alright I suppose you could look at it that way.

 

-- Chuck

 

Point is the recommended viscosity is a 1999 spec single grade SAE 90 GL5/6.
If one could go to any automotive store today and still get exactly that, there would be no discussion (or less...)
So one has to translate '1999 spec single grade SAE 90 GL5/6' into 2018 gear oil.
Unfortunately Google Translate does not work for this.
The most acurate translation in my opinion is SAE 110, 75W110 or 75W140.
Because of the GL6 in the original the modern 75W90 oils are out.

And NO, one CAN NOT apply 'thicker is better' for the engine.
Engines use oil in a completely different way compared to a differential.