Mixing differential oils?

[t0ad]

So over the weekend I poked around on my LGT and noticed that when totally cold, my front differential dipstick reads just a hair over the L mark. I guess my first question is, is that okay for a totally cold reading? It's kinda tough to get in there and check when things are warm.

 

Second question, since I bought the car used, I have no clue what's in it, fluid-wise. I can only assume it's still the original fluid from the factory, as the car only had 28k on it when I bought it. Now, would it be alright to go grab some OEM stuff from the dealership and top it off? What about other brands of 85W gear oil?

 

Or should I just drain both diffs at 30k and replace with Redline

[Xenonk]

1) yes, but you can add another 1/2 qt in.

2) you're ok with mixing.. but at 28k, it's time to change it out anyways.. a lot us just buy 75w90 NS Redline tranny/diff oil..

 

(edit: I just noticed that you are from WV.. I will be up that way at Summit Point this whole weekend and Friday running the GT on the main circuit with a few other Subaru owners, come up and watch if you have the time).

[t0ad]

Cool. I remember reading a big thread about tranny/diff oils .. ended up rather confusing. 75w90 NS in the rear diff since it's limited slip, so should the front diff (auto) use regular 75w90? What about the tranny?

 

I had no idea Summit Point existed until I read about it on here. Sucky thing is it's way over on the panhandle, which is like 300 miles from me

[mbacis]

From the service manual (differential oil replacement section):

NOTE:

Each oil manufacturer has its base oil and additives.

Thus, do not mix two or more brands.