2021 Subaru Crosstrek 6MT transmission and differential oil

Mar 27, 2009
I need to change the transmission and differential oil in my 2021 Crosstrek with a 6 speed manual transmission. It looks like Redline 75w90NS is the fluid to use for the transmission.

Since the Crosstrek has an open rear differential, would the 75w90NS be a better fluid than their regular 75W90 gear oil for the rear differential? Is there any advantage to using their regular 75w90 with anti slip additives or would the "NS" version provide better lubrication?
I believe I ran the same 75w85 in the trans and diff in my 2018 Forester - would be the same trans and rear differential. Seemed to work fine with no issues.
There is a special socket to drain the trans. You might need to buy that.
I think most newer Subarus use the Subaru Extra MT gear oil in the manual transmissions as factory fill, which is a 75W80. 75W90 is listed as an acceptable substitute, but keep in mind that the thicker fluid will make the gearbox more sluggish in cold weather and reduce fuel economy a bit. The only common substitute in a 75W80 is Motul Motygear, which I hear is good in these transmissions.

Redline doesn't recommend using the 75W90 (non-NS) in most transmissions "since the extreme slipperiness may cause synchronizer mesh issues that lead to shifting problems". Use the NS version in the transmission if using Redline. Either version is fine for the rear diff. Motul 300 is also a good full synthetic that I've heard gives better gearbox feel than Redline in Subarus.