[bender rodriguez]

I know rear diff is Mobil1 Synthetic Gear Lubricant LS 75W-90 but not sure about manual trans.

[PhaseP]

The oil type (BMW designation) should be written on a sticker on the side of manual transmission, if it still hanging in there.

Mine, an early XI, had MFT-LT-2 from factory, 75W80 GL4

http://www.ecstuning.com/BMW-E90-325...3.0L/ES197386/

Used this one during replacement, I suspect it is same thing as the OEM LT-2, but not 100% positive. Shifted the same after replacement, around 60K:

http://www.ecstuning.com/BMW-E90-325....0L/ES1893847/

[bender rodriguez]

Originally Posted by PhaseP

The oil type (BMW designation) should be written on a sticker on the side of manual transmission, if it still hanging in there.

Mine, an early XI, had MFT-LT-2 from factory, 75W80 GL4

http://www.ecstuning.com/BMW-E90-325...3.0L/ES197386/

Used this one during replacement, I suspect it is same thing as the OEM LT-2, but not 100% positive. Shifted the same after replacement, around 60K:

http://www.ecstuning.com/BMW-E90-325....0L/ES1893847/

Redline, royal purple and mobil1 do not make a 75w80. So it is safe to assume 75w-90 is fine?

[PhaseP]

Redline has an application guide which you can find what they recommend:

http://www.redlineoil.com/application.aspx

They recommend automatic transmission fluid for my car, you can check yours.

It doesn't seem as simple as the viscosity ratings.

[bender rodriguez]

Redline costs too much. Ended up getting 5 qt of mobil1 75w-90 for 40 bucks and they meet GL-5 spec which bmw says is fine.

[PhaseP]

Originally Posted by bender rodriguez

Redline costs too much. Ended up getting 5 qt of mobil1 75w-90 for 40 bucks and they meet GL-5 spec which bmw says is fine.

I don't know, the transmission or the differential(s) are much more expensive than once in a couple of years fluid costs. Why risk it?

Not much knowledgeable but I hear some manual transmissions having brass synchros are not compatible with all gear oil, even though it is same spec.
Also differential oil probably has different friction elements than manual transmission oils. Differentials don't have synchros to worry about.