Switching from ATF to CHF 11S in BMW P/S

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Yes, switch from the cheap ATF fluid to the expensive CHF 11S. I have a newer 335i that specs CHF 11s and a daily driver '03 530i that specs "ATF"; aka Dex III. I'm well aware of the Dex VI being newer, and mainly thinner. And some manufactures going to it for p/s fluid. However, I'd like to take it a step further and completely flush my ATF ps system out and run the super thin CHF 11S and stock 1 product for both cars. And maybe free up some power/MPG's while I'm at it. Is that possible or am I going to completey ruin my old ATF p/s system bying flushing it over to CHF 11s? I could play it safe and just flush it over to Dex VI. Middle of the road on visc.
 
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Coldtown, Canada
That's really hard to say; but I will say that I've been debating trying the same thing myself. I want to go to a thinner fluid to encourage better cold weather performance, free up the engine, and potentially get a little heavier steering feel. I will say though that a power steering pump for the most part lacks complicated bearings that require thick fluid to protect operating surfaces, sort of like how an air conditioner compressor only needs a very small amount of relatively thin fluid. But I'm no expert. I could easily say its probably fine, much like running thin fluids in a lot of hydraulic equipment is fine (at a loss of power and equipment feel), but a PS system is difficult to really give any input in on such an experiment.
 

JHZR2

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You say some OEMs are specifying Dex VI in PS systems? That's news to me. Id really just ask why. It is so easy and cheap to get a quart of ATF, and a good syn ATF will work great. Ive been using the same M1 ATF in my E30 reservoir for a long while now. Works fine. Seems overly complex of a job to get it all right (not sure of the compatibilities, isnt 11S incompatible even with the 7.1 fluid?) when ATF, even good ATF is so ubiquitous.
 

4x4taco

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FL
^ Nissan/Infiniti are using it along with GM. Dex VI factory fill p/s fill. I agree that maybe going the CHF 11S is a bit over the top with so many questions of seal compatibility and cost alone... $20/liter @ Napa. $26/liter @ BMW. Same bottle. M1 ATF is $10/qt. I can get Castrol or Valvoline Dex VI for $7/qt and it's thinner. Valv is saying thiers is full syn. Castrols is syn blend. I think I can get the castrol for $1 cheaper @ AAP. Or maybe Walmart. Yeah... I think I'll play it middle of the road on cost and safety and just doa Dex VI. Plenty of people have done that w/out issues.
 

JHZR2

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You mention seal compatability, but Id be concerned with this using Dex VI too. Reading in the ATF section on here, apparently it is an issue with elastomers in some ATs too. No GM Ive ever owned has specified ATF of any sort as PSF... But thats another discussion...
 
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Regina, Saskatchewan, Canada
Originally Posted By: JHZR2
You say some OEMs are specifying Dex VI in PS systems? That's news to me.
Yep, that's in my G's manual, along with the alternatives of Nissan Matic J (or presumably S) or Nissan PSF. The filler cap just says Dexron, but the book says Dexron-VI.
 

MolaKule

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Quote:
Yes, switch from the cheap ATF fluid to the expensive CHF 11S
The Pentosin fluid should do very well with any material in the PS system and perform better in cold weather.
 
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GM has at least two TSBs regarding situations where DexVI should not be used (04-07-30-037C & 04-07-30-037D). The second TSB (2008) states to discard the first. The recommendation for PS systems was NOT DexVI. It was PS fluid. From page 1 of the second TSB, "Power Steering Systems should now use P/N 9985010 labeled Power Steering Fluid." However, GM Techlink (May 2009, Volume 11, No. 5) says "power steering systems should now use p/n 89020661 (89021183 in Canada) Power Steering Fluid" but cites the *-037D TSB. There is an inconsistency in part numbers for PSF, but as of 2009, all guidance from GM for GM vehicles was to use a PSF in PS systems, not ATF.
 
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sweden
I have actually done this in 2 cars, one houndai and my pt cruiser. I simply used a turkey baster and sucked it empty a couple of times. I did it because the original fluid looked like [censored] and i could get chf cheap ( othervise it would have been atf+4 going in there.) I did this 2 years ago and what happened? - No problems what so ever... - No change in steering " feeling" No noticeable change at all, but the fluid still looks like new so i feel better....
 
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