Dexron III or CHF11s power steering ATF?

[Spaceturtle917]

Before you ask I've searched the forum.

I'm going to change my power steering fluid. I have a 7/1990 535i and there is no label on the lid or anywhere on the reservoir or in the engine bay. Someone help me out here, I'm assuming it's Dexron III.

[BleedsBlue]

ATF (DIII) is 99% likely. The fancy stuff was mainly in SLS cars. This is of course assuming that your car has original or like parts.

For a little better idea, you can also see what color the current fluid is (though of course, ATF does exist in the same color as CHF...and sometimes it's just brown/black, and of little help). And no worries for asking, this topic is contentious.

[Spaceturtle917]

I think I remember the previous owner topping it off with ATF when I was looking at it too. Also is red. I picked up some Valvoline Synthetic Dexron III.

[moroza]

Previous owner's choice doesn't mean anything. Mixing the two fluids results in leaks. Pentosin seems to be a transluscent greenish color from what I've seen, while Dex ATF is red.

[fo3]

On my 9/1990 525 the cap said pentosin 7.1. There was ATF in it when I bought it and the steering was loud and 'chattery'. First thing I did was flush through some synthetic PS fluid designed to replace pentosin and it immediately quietened up the steering. So it's not just the fancy sls and top models that use pentosin, it could be a 1990 and earlier thing.

[BleedsBlue]

Previous owner's choice doesn't mean anything.

So it's not just the fancy sls and top models that use pentosin, it could be a 1990 and earlier thing.

^This is why I made sure OP didn't feel bad for asking. There are a million threads but no definitive playbook, unfortunately. I'd heard of early cars with Pentosin in them, as well.

At least if there are no leaks or other side effects, continuing to fill with what the P.O. used should be a safe(r) bet.

[fo3]

There will be leaks, That's why the PO was probably resorting to cheap ATF. That's why mine did A vicious cycle of chuck it in there because it's cheaper, oh it leaks, keep topping up with ATF because it's cheaper...

[BleedsBlue]

^Extremely fair point on an old BMW

[Spaceturtle917]

I’m pretty certain it was atf. Old fluid was red. Ran quiet and gave me no issues with leaks. I haven’t gotten the new fluid in yet but I think everything’s gonna be alright.


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[Billyj]

Either fluid will work assuming the system is flushed correctly.

I almost always use ATF with my bimmers atf was just n mine when I bought it.
Atf will work without noise or issue

[CarterH]

I recall reading that every E34 used ATF and only the ones with self leveling suspension used CHF11. The color of the fluid should be enough to go by too.

[ross1]

reservoir type is a good indicator too. The plastic reservoir/cap typically use dexron and the metal can/lid with a strainer use Pentosin. I've heard of exceptions but never seen it for myself.

FWIW I once had the distinct pleasure of changing the steering rack and resealing the P/S pump of an Audi 5000 asking for Pentosin that had been filled with ATF, it leaked from every pore. While the system will operate with other oils some seals won't suffer ATF very well.

I know a guy who peed into his master cylinder, his brakes worked well enough to get him home but that doesn't make it the correct fluid.

[GregT53]

I thought all E34s with SLS use CHF 7.1, which is mineral base. CHF 11S is full synthetic and not to be used in an SLS system. The tightening knob on top of the reservoir is marked with the correct fluid specification. Of course, on a 20+ years old car that knob may not be original so you can't be absolutely certain. My '95 525 takes ATF and is so marked. My '93 M5 takes CHF 7.1 and is so marked. CHF 7.1 is no longer made by Pentosin. Febi M6162 is CHF 7.1.

[BleedsBlue]

None of these methods are foolproof, though they are correct.

1) Not every E34 sans-SLS uses ATF, I've seen a few myself with what looked like original reservoirs
2) I've also seen the "wrong" fluid in one or the other reservoir
3) As Greg qualified, the cap is usually no longer marked (at least correctly)

Not saying any of these are valid or good reasons, I'm just noting why the confusion persists. Most of it, as always, comes down to human error in terms of previous owners or garages.

I think it is likely that every non-SLS E34 would have had ATF from the factory. However, with a proper flush, you can still use the fancy stuff (see my 1) above. Important note is that it won't mix with ATF....and is more expensive.

Technically, 11S (which was replaced with 202) was specced for 9/91+ BMWs. You can use the full synthetic in an SLS car-- both BMW and Pentosin say that, it's just a matter of a proper flush because the mineral 7.1/Febi 6162 does not mix well with the synthetic stuff.

I've heard and read hearsay about the power steering pump being affected by the fluid, but am uninformed as to the specifics.

[moroza]

Either fluid will work assuming the system is flushed correctly.

My understanding of the specifics is that the two fluids (Pentosin and Dexron) chemically react with each other in a way that softens and weakens rubber seals, causing leaks. Uncontaminated rubber is compatible with either fluid, but once a system has seen one, using the other, even after a full flush, is rolling the dice on leaks from hoses (if you're lucky) or the pump or steerbox (if you're not). Same idea as changing the AC from R12 to R134a: the hardware is (mostly) compatible, but mixing even traces of the fluids is risky for the seals.

I recently worked on a 94 (?) 540i that came with Pentosin but some PO had replaced with ATF. The two short hoses between the cooler lines and the other hard lines, located near the port-side bumper shock, could be moved back and forth on their nipples with light finger pressure, despite factory crimp-type hose clamps still clamping the very swollen rubber. Needless to say, it leaked like an intelligence agency.

Fun fact: the original Dexron 1 was made in part from whale oil.

I know a guy who peed into his master cylinder, his brakes worked well enough to get him home but that doesn't make it the correct fluid.

Quoted For TRUTH

[fo3]

9/1990 build 525 with original cap and sticker
SAM_1600.JPG

I think the fancy and high spec SLS ones with metal reservoirs used chf11. But some early regular e34s used chf7.1 with plastic reservoirs.

[fo3]

From the BMW Operating Fluid Guide I found:

BMW Operating Fluids

3.0 Ball and Nut or Rack and Pinion Power Steering

Only reputable brand Automatic Transmission Fluid (ATF) of Dexron® III formulation may be used for the power steering and power steering pump.

In case of brief hydraulic noise after starting at low outside temperatures, we recommend replacing the red ATF with green CHF or LHM oil (see below).

4.0 ZF Ball and Nut Power Steering with H31 System

The approved oils for BMW models with power steering and the H31 brake booster system are identical with those oils approved for power steering without the H31 system except for the following:
E32 models with self-leveling rear suspension and mutual oil supply tank in the engine compartment (see Group 37 Integrated Suspension Systems).
Countries with very low outside temperatures (e.g. Canada) had their power steering systems filled at the factory with Pentosin CHF 7.1 since 9/87 through 9/91.

This is also to be used on vehicles built before 9/87.

Since 9/91, vehicles now use Pentosin CHF 11S instead of CHF 7.1.

Pentosin CHF 7.1 BMW Part No. 81 22 1 468 879
Pentosin CHF 11S BMW Part No. 82 11 1 468 041

These cars are marked with a pertinent label located close to the oil tank.

LHM oils (green color) of the following manufacturers may also be used instead of Pentosin (CHF 7.1):
Shell LHM
Castrol LHM
Exxon LHM

The mixing of CHF, LHM oils and ATF is not permitted.

Pentosin CHF 4548 was used on vehicles built before 9/87 but is no longer available. However, mixing of Pentosin CHF 7.1 with residual quantities of Pentosin CHF 4548 are permitted in these earlier vehicles. Mixing of these two oils is not permitted for E32 / E38 vehicles.


The hydraulic system for power steering and power-assisted brakes must be drained as completely as possible when changing from one type of oil to the other.

All oil supply reservoirs are marked with the type of oil being used — ATF or CHF.

So really only pre87 or cold country exports should have pentosin chf7.1 if you don't have SLS. No idea why mine does. They must have raided the parts bin for RHD exports to Australia.
(Storeman/accountant" We have too much left over CHF7.1 and stickers". Boss "just send it all to Australia, they're paying double the price for the car anyway, so what are they going to do? Tell them it's for hot weather."

[ross1]

From the BMW Operating Fluid Guide I found:


So really only pre87 or cold country exports should have pentosin chf7.1 if you don't have SLS. No idea why mine does. They must have raided the parts bin for RHD exports to Australia.
(Storeman/accountant" We have too much left over CHF7.1 and stickers". Boss "just send it all to Australia, they're paying double the price for the car anyway, so what are they going to do? Tell them it's for hot weather."

I wouldn't put it past them.
You guys do take a shellacking down there.

- - - Updated - - -

Fun fact: the original Dexron 1 was made in part from whale oil.

As was the "good stuff" limited slip additive.

[Spaceturtle917]

Lot of good info in this thread. ATF worked fine. No leaks, smooth steering and no noise.


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