STi owners: What transmission fluid do you use and why?
 

Looking for recommendations on transmission fluid for the STi transmission... seems to not be as picky as the WRX 5MT... I have read on numerous occasions on nastysock that Redline Shockproof is not recommended because of the internal pump on the 6MT, and that dino oil should be fine... but what do YOU think? Others I have heard mentioned are Redline 75w90NS, Mobil 1, Royal Purple...
Bryan

I had this same problem.

When I went to Xotic Andy said, "well Dimitri, I use this Castrol Syntec synthetic oil." So I said, "well how many do I need and how much?" lol

If that's what he is using in his car then it's fine by me. lol I remember Greg using GM synchomesh but his tranny was all sorts of ****ed up, grinding, rattlin, and I don't know if that changed with the gear oil.

All of the threads on NASIOC about the 6MT are littered by 5MT owners just totally confusing things since the two transmissions are completely different.
Sounds like the factory fill isnt a bad way to go, or the Redline 75w90NS... just keeping it simple since there's really not an issue with the transmission in the first place.
If anyone has any other experiences, let me know... its just that I realized today this was a very important component of my install on Sunday...haha.

The best caktail (damn filters) I've found is the 1 qt of Redline Shockproof gear oil (I think that's kinda close to the product's name) and fill the rest with the Redline 75w 90s. I've run that for about 20K miles so far and no complaints at all. I'm convinced the Suby 6mt is the smoothest shifting awd box you can get.