Question about power steering ...

[OmarE34BMW]

Hey guys
so my power steering has been making this awful sound turning at low speeds (like a whine) and I assumed the PS fluid was low. After opening the resevoir, I noticed it was almost empty, (about an 1/8 full). So until I find I find the leak, I wanted to just fill it back up to get rid of that terrible noise. My question is what to put in. According to this site http://www.bmwe34.net/E34main/Maintenance/Steering/PS_fluid.htm there are 3 different fluids that go in to the e34 and the sticker on my cap is rubbed up so I dont know which one to purchase.

The car is a 1991 525i by the way. I figured I'd go ahead and do an oil change this weekend also but it'll be my first on this car (just purchased a few months ago). Is there anything special I need to know or is it typical oil change procedure? I there any trick to removing the filter without dropping oil all over the place? The diy I looked at claimed that there will basically be oil everywhere once removed as it sits in an upright position.

Thanks in advance.

[ross1]

99% sure yours is ATF. The reservoir ought to have a label indicating which fluid to use. If it is a knurled plastic cap ~2 1/2" then ATF, if a small knob that retains a metal lid ~4" across then "Pentosin". Pentosin won't harm a system intended for ATF but ATF in a Pentosin system degrades seals. Don't be tempted to use ATF in a $25/qt. Pentosin system, you'll end spending way more for repairs.