The Difference between ATF & PSF?

Status
Not open for further replies.
Joined
Dec 27, 2005
Messages
577
Location
Chicago
I need to know what's the difference between the two? All three of my cars say to use ATF, but when I went to Lubegard they make a "Claim" that PSF is better that ATF for power steering geaboxes. I understand that keeping the oil accessible to the consumer, ATF is easy to get. So please explain the whys and what nots.
 
I don't know the specifics. I got a PS flush a year ago. The place just used their bulk PS fluid, even though the car calls for Dex III ATF. I found out their supplier, and called the company and got to talke to one of their chemists. They said it "shouldn't" cause any problems because they are similar (ATF and PS), but if it calls for ATF to probably use ATF. So I went back to the shop and they redid the flush, this time with ATF.

I also suctioned out a few ounces of fluid when I got home and put in some Lubegard PS fluid protectant (purple bottle). Before doing so, I called LG asking to make sure their PS was good with ATF. They had to call their lab to find out, and they sadi it was. Been a year and no problems. PS is better than ever, actually.

Moral of the story: if it says use ATF, use ATF. And the LG PS addative should work with either ATF or PS fluid.
 
I would rather have a high quality, syn ATF in my power steering than regular PSF, even if it calls for psf. But in a honda or acura, def use something compatible. I think the main component of ATF that might not be needed or present in PSF would be the friction modifiers for clutch engagement.
 
If yours call for ATF then I would use it. I use M1 ATF for years now and have never had a pump fail.
 
In some cases the difference is just the lack of red dye in the PSF. In other cases there is a different additive package in the PSF (Honda and others), and there isn't much info around about this.
 
Originally Posted By: Ken2
In some cases the difference is just the lack of red dye in the PSF. In other cases there is a different additive package in the PSF (Honda and others), and there isn't much info around about this.



The Lubegard PSF address this issue.

http://lubegard.com/~/C-199/LUBEGARD+Power+Steering+Fluid
 
Originally Posted By: boxcartommie22
i like red lines power steering fluid over atf


Same here!
thumbsup2.gif


This stuff just refuses to boil over at the track (road course).
smile.gif
 
A bit of history here.

First, power steering fluids (PSF) and ATF's are both hydraulic fluids because they are used in specialized hydraulic systems.

The early PSF fluids were simply mineral-based oils with a low-level phosphorous-based, or a low level of ZDDP addtives with a calcium detergent additive and anti-rust, and metal deacctivators. Specialized fricton modifiers were not needed in PS systems as they had are no friction clutches, just valves, racks, gears, seals, and hoses. Anti-oxidants of course are needed to stabilze the oil against high temperature fluid degradation.

Notice that both PS and AT sstems are essentially closed systems that do not see any combuston gases, so the addtive package and viscosity (thickness) are very different as compared to IC motor oils.

Modern ATF's have wet clutches, which required specialized friction additives to allow smooth shifting during clutch engagement/disengagement. Early ATF's were also mineral oils with low-levels of anti-wear additves mainly for the benefit of the sun/planetary gearing. In addition, low levels of detergents and dispersants are needed only to keep the internals clean. Anti-rust, and metal deactivators (especially the copper deactivators) are needed to keep the heat exchanger (cooler) metals from corroding. Anti-oxidants are needed here as well to stabilze the oil against high temperature fluid degradation.

Later, it was found that ATF's could funtion well as PSF's and it also reduced dealer inventory. Any Dexron/Merc or Type-F ATF seemed to function well as a PSF.

All was well until Honda and GM started requiring PSF formulations because of specific PS designs.

The mineral oil based Honda PSF's required high AW additive levels because of their design or design flaws inherent in the PS design.

The new GM PS fluid is essentially a very low detergent PSF, mineral-oil based fluid with a low level Boron/phos AW additive package.

The Dexron VI fluid was the first low viscosity ATF fluid (6.0 cSt), but this is only the beginning. Vehicle manufacturers are now using or developing transmissons that use fluid viscosities down to 4.0 cSt or lower.

But PSF fluids are still being specified at 7.5 cSt viscosities.


Additives:

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=530321#Post530321

Here is a companion thread:

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2239916#Post2239916
 
Last edited:
Thanks MolaKule that info certainly helps alot. I'll try using PSF on my Infiniti Q45 instead of ATF. Any more on this subject PLEASE chime in.
 
The following post was meant for here but somehow got incorrectly dumped into an ATF post, so here it is:

Quote:
Look at your operators manual under fluids.

If your GM vehicle specs the newer GM PSF fluid #89020661 I would highly recommend using an Over-the-Counter mineral oil-based fluid or the new Amsoil PSF. The Amsoil PSF is more closely related additive-wise to the GM fluid than the Redline PSF.

The GM PSF fluid #89020661 is a low detergent fluid with a special S-P AW package.

The Redline PSF has an additive package more suited for manual transmission/transaxles that specify an ATF-like fluid at 7.5 cSt viscosity.

From Redline:
Quote:
This fluid also satisfies power steering units requiring GM PN 1050017 or 1052884 (Spec Number 9985010), Chrysler Spec Number 5931, and Ford Spec Number M2C33-F. It also satisfies the hydraulic specifications of Denison HF-O, Vickers vane pumps, and Sundstrand piston pumps.


Notice, this fluid DOES NOT cover the GM part number #89020661!

If you have an older GM vehicle and it specifies an ATF, then Redline D4 or any DexIII equivalent, or Ford Type "F" fluid should perform just fine.
 
Last edited:
At Tires Plus and Tire Kingdom, we were always sent fluid which said it met each P/S system need, and we used that. We never had problems caused by it.
 
Status
Not open for further replies.
Back
Top