Mine is pentosin. Says CHF-11s ONLY on the cap. If you search for my name, i posted a thread on it a while ago, with a picture.

People use ATF instead of Pentosin when they have a leak in their system and find out that the cost of a liter of Pentosin is more than 4 time the cost of ATF. At least that is what they do on the Audi forum.

CHF-11S Green ---> Red Rusty color
 

Question for the gurus re Pentosin color...

Just sucked some of the old PS Fluid out (about 100 cc), it was Red Rusty color, similar to the color of standard Dexron-III fluid. Then filled with Pentosin CHF-11S, which is green (the PS cap says use CHF-11S).

The X5 was serviced by dealer over the last 9 years by P.O.

CHF-11S ($19.50 at Napa Auto Parts) has Green color.
From my reading on the web, apparently this Green color turns to Red after some miles? Is this true?

I am attaching a photo so you know what I am talking about...

Hmmmm, if your cap says CH11S then I'm assuming thats what should have been in there. Who knows what the dealer was actually putting in though...

My e32 735iL had rear SLS and used CHF 7 (which was the hydraulic non-synthesized fluid used prior to CHF 11 S)..and it too was green...and remained green unless someone poured another color fluid into the reservoir.

But more than likely what has happened is...over the last decade...the original ATF PS reservoir cap has been discontinued by BMW...and it's replacement is the CHF 11 S cap (which fits). When the change-over first occurred...peel-n-stick labels where available to adhere somewhere on or near the reservoir or cap to indicate that the reservoir actually used ATF and not CHF 11 as indicated on the cap.

I believe the replacement caps now sold for lots of old & new BMWs use the same PS reservoir cap...BMW part # 32 41 6 851 332. If you run that nbr through the part cross reference...you'll see how many different old & new BMW models use this same cap...some that may use ATF and some that may use Pentosin...and you need to purchase the label to indicate the vehicle requires ATF if you buy the replacement cap.

So, if your PS reservoir is filled with reddish pink fluid...more than likely you have a replacement reservoir cap. Because the only e53s that may have come with Pentosin CHF 11 S would be the ones sold in areas near or above the Arctic Circle...where the Pentosin fluid can withstand the severe cold of that part of the world.

Take note of the supplemental info in the part database as well as the line below #1 & #2 that is for a LABEL for oil carriers that use ATF...that's because BMW only makes the one PS lid now:

My PS Cap clearly has the "CHF-11S" engraved in it, no sticker.

I searched autohausaz.com and rmeuropean.com, both of these websites list Pentosin CHF-11S as the the fluid.

My theory (and my reading somewhere) says that the Green color turns into red rusty during service. Can someone verify this Color Change?

Interestingly, my 2005 Volvo XC90 2.5T PS cap also says CHF-11S, yet the fluid inside the reservoir is golden brown (or reddish). So I am leaning toward color change as normal behavior of the fluid, maybe the green dye dies with heating process.

I just googled "pentosin green brown", and see some interesting posts...

the fluid should be a nice clean card red OR a semi-clear green color. If itsd any other mix, like a brick red, that means someone mixed both the pentosin 11S anbd ATF hydrauylic fluids and tihs is a bad idea. the PS system needs to be FLUSHED and maybe put the Pentosin (brand name) CH-11S fluid inm, as the cap dictates.

For kado1976
To complement what was posted and shared. VITAL to not confuse which fluid to use (ATF vs. Pentonsin). As it seems that your 3.0 L E53 is ATF (same as my former 3.0 L diesel), I would highly recommend Redline ATF and better still the Redline Power Steering fluid (a variant of ATF). Better component life and NO groaning when cold (I can attest to this).

When I first bought my E53, I used Pentosin. Like 4 bottles. It was pricey so I replaced the hoses and housing. After searching here and realizing the cap said ATF, I went to DEXIII. DEXIII is no longer made. DEXVI is equivalent.