I know Red Line says to mix away, you can use any of their GL5 gear oil in any % you want to use.
They even say to mix 75/140ns with mt 90 or 75/90 to bring up the vis. on their web site

75W140NS GL-5 GEAR OIL

• Option for noisy transmissions when mixed with 75W90NS or MT-90 to bring viscosity level up
• Also used in clutch-type limited slip differentials in racing for maximum lock up-some users add Limited Slip Friction Modifier in small doses to customize slippag
  https://www.redlineoil.com/75w140-ns-gl-5-gear-oil
  
  I got a E mail from Red Line 6 or 7 years ago that said I could mix their MTL, MT85 or MT90 to get the right viscosity for my transmission and thats what I do for my S.

ROD

 

I also called Redline several years ago to ask what I should use because I had too much MT90 on hand and a couple of MTL. The guy I spoke with told me that while MT90 was too thick to be used alone in the Sk2's tranny, I could use 1 QT of MTL and top it off with MT90.

 

I'm just gonna leave this here...

 

I just have send a mail to Motul.

 

Oh yes, they are the best tire I've used so far.
The front/rear ratio of the AD08R's is different than the original S-02's (the AD08R fronts are percentage-of-the rear wise substantially wider than the front S-02's) so I did change the OEM front sway bar for a Whiteline (= stiffer) to compensate.
And as far as I'm concerned that worked, in combination with the Koni Yellows on pretty much OEM ride hight I think the car handles better than original.
The alignment is UK-spec but without the rear toe-in listed in that spec, that's way to much as 'we' concluded in a thread in UTH a while ago (it must be still out there)
And replacing all those rusted solid bushings & pins helped too: no hidden pre load and butter smooth alignment, even after 10 years.

Are we going to turn this into a suspension thread now?
Haha!

 

They know their product better than any.
If you KNOW your oils share ALL the additives and ONLY the base oils are different, then sure.
Do you have any info on that, MSDS's?
Going by what Mr.matchbox posted where was mentioned the one oil has this sulphur smell (and the other one does not I assumed, later showed by MSDS) they for sure have a different additive package.
Mixing in that case dilutes additives and that's bad... mmmkay.

 

whats your opinion on regular (i dont know the correct word) vs sythetic oil for the diff?

 

whats your point man? What does your msg#32 have to do with the email from Torsen? And what is "atf" fluid?
whats your point?? Just be clear. Thanks

 

No we're not and just to avoid other posters getting annoyed we'll stop here lol.

Glad to hear about the AD08R's. Fantastic (140...?) TW tire! Definitely on a higher level of grip/performance than the OG S-02's and even my Toyo Proxes T1S. I may consider running a set of 08's for the track or at least the rear end since I have a spare set of rims.
I too run Koni Yellows but with Tein S Tech springs. Great combo and she definitely handles better than stock with more lateral grip/stability and higher g's during hard cornering. That being said originally she handled damn good.

Back to oil

 

The word is "mineral". Mineral oil generally doesn't flow as well/fast as synthetic and doesn't have the same additive packages as synth oil however I think that applies more to motor oil than diff/gear oil although, I could be wrong. Actually why wouldn't it apply to diff/gear oil now that I think of it...
In general its best to run synth all round. That being said I picked up that bottle of Liqui Moly I posted here and it's GL5 hypoid, LS oil all that jazz but is mineral hence the lower price tag. It's been sitting around unopened for months. Now I'm wondering whether I should throw it away and just splash out on the synth variant...

Synth oil comes from a higher refined base oil as well. Can go longer than mineral oil without breaking down as early.