old debate: PSF or ATF for power steering system

[mikeinaustin]

Yep it has been discussed since time immortal. The manufacture says use A and people use B. Having just had a steering leak, i started wondering about this again.

So toyota (my case) specifes dexron ii for the power steering system fluid. however, over time, the components of the system change: hoses get replaced, power steering pump gets replaced, etc, etc. I suppose if you only use toyota parts dexron ii will be the fluid, but if you don't and use things from napa/autozone/etc do those replacement seals/rings/etc really really need dexron ii versus PSF? (or vice versa depending on your vehicle)

Personally i always used mobil 1 atf or amsoil atf in my system figuring it was a higher quality fluid. but really, i don't know the difference between true psf and a synthetic dexron atf.

your thoughts?

 

[RedCorvette]

Seeing that power steering fluid changes are not on most maintenance schedules, it seems to be a very uncritical fluid to change, and thus using ATF or PSF would similarily probably be an immaterial decision.

Having said that, I would always use what the manufacturer recommends.

 

[EricF]

I try and use what the mfgr specs.

 

[NHGUY]

GM always wanted PSF,Chrysler always stated "Never use transmission fluid",then they switched to ATF+4.Ford used to say Type-F,then went Dexron,Mitsubishi is Dexron,Audi wants mineral oil,Honda is special....so,everybody wants something different.Its not the 1960s anymore!

 

[RF Overlord]

You need so little of it and change it so infrequently that cost should be immaterial. Just use what the manufacturer calls for.

Just to add to the confusion, my '94 Thunderbird SuperCoupe called for PSF, but my '03 Marauders call for ATF.

 

[Loobed]

Originally Posted By: mikeinaustin


your thoughts?




The Power Steering is system is a hydraulic system. ATF is a hydraulic fluid, but that doesn't mean all hydraulic fluids are the same. Cheap power steering fluid costs about the same per qt as cheap ATF.

I use Power Steering fluid in my truck. I change 1 pint @ every oil change. If I needed to add fluid and didn't have any PS fluid on hand, I would use ATF.

 

[Hokiefyd]

Originally Posted By: mikeinaustin
So toyota (my case) specifes dexron ii for the power steering system fluid. however, over time, the components of the system change: hoses get replaced, power steering pump gets replaced, etc, etc. I suppose if you only use toyota parts dexron ii will be the fluid, but if you don't and use things from napa/autozone/etc do those replacement seals/rings/etc really really need dexron ii versus PSF? (or vice versa depending on your vehicle)


Nobody has gotten to the crux of your question, which is a good question I believe. How is power steering fluid different from ATF, and what components in the system are primarily driving the requirement for one vs. the other? And if those components are changed out for aftermarket components, how does that impact the fluid requirement?

I think it's a great question. You're not trying to make a decision about cost or value. You're trying to understand what is behind the requirement for one fluid vs. another. And I don't know the answer either, but I do hope we find it.

 

[wirelessF]

GM vehicles call for PSF, don't know what is really is but it's not like ATF. Toyota calls for a DexronII, which is an obsolete ATF fluid but it tells you to use an ATF. In my case I use Dexron VI in my toyota tundra's power steering.

IMO those bottle of PSF they sell at stores are for just GM vehicles. Then your Honda/Acura fluid. Then your ATF fluid for transmissions and power steering systems that call for ATF.

 

[Wilhelm_D]

Originally Posted By: Hokiefyd
Nobody has gotten to the crux of your question, which is a good question I believe. How is power steering fluid different from ATF, and what components in the system are primarily driving the requirement for one vs. the other? And if those components are changed out for aftermarket components, how does that impact the fluid requirement?


It rather depends on which PSF you're talking about.

Chrysler at one time used a PSF because their power steering differed from everyone other company's power steering.

Honda and Accura have used a highly friction modified and viscosity stable power steering fluid for several years.

Some of the European manufacturers use a low-viscosity fluid with an extremely high viscosity index.

 

[tig1]

I have used M1 ATF in my PS pumps for many years with excellant results in all times of the year.

 

[Loobed]

Here is the PDS for Redline Oil's power steering fluid and ATF

http://www.redlineoil.com/content/files/tech/Power Steering Fluid Product Data.pdf

http://www.redlineoil.com/content/files/tech/ATF PDS 1-10.pdf

you can see that there is a difference. It "looks" like ATF might be a multi-grade type fluid while the PS fluid is a straight weight fluid.

Someone with more knowledge of hydraulic fluids would know better.

 

[tommygunn]

My Chrysler in 1997 called for only a Mopar-specific PSF (and absolutely NO ATF). Later, factory fill was changed to another type of standard PSF. Later again, it changed to ATF+4 (ATF).

A TSB states that topping off or replacing the second standard PSF with ATF+4 is acceptable now, but under no circumstances should the original Mopar-specific PSF be mixed with ATF+4.

To compound the issue, it states that if the entire steering rack is drained, its appropriate to replace all the PSF fluid with ATF+4 in all cars (even if it shouts NO ATF at you). The same TSB however states that under no circumstances should ATF+4 be used in certain cars (which varies greatly, some it recommends only the old Mopar-specific, some it recommends ATF+4, even if the racks are identical in type and years).

To again make life difficult another TSB for my car states that if there is cold-weather performance issues, the fix is to drain the rack of the old Mopar-specific fluid at the cooler and put in ATF+4 (again, contrary to the shouty NO ATF in the original manual).



So what does this all mean?

I have no idea and it sounds like Chrysler doesn't either. I drained it completely to avoid mixing types and filled my car with ATF+4. It sure feels better when its cold (and I expect it has better cold properties then regular PS fluid) and so far hasn't exploded. So I'm happy.

 

[Texan4Life]

power steering is a basic hydraulic system. just about anything will work. use what works for your. if you have probs, try something else.

I'm running M1 AFE 0w-20 in my 90 deville PS for about 20k miles now and couldn't be happier.

 

[mechtech2]

Fluids may not mix, but that is not the same as either one not being entirely suitable on it's own.

Honda historically HAD to have it's own fluid.
There are others, now.
ATF was almost universally used as a fill or flush, years ago.
If our cars spec ATF, we are just lucky to have a cheap and readily available fluid for them.

 

[MolaKule]

Quote:
Here is the PDS for Redline Oil's power steering fluid and ATF

http://www.redlineoil.com/content/files/tech/Power Steering Fluid Product Data.pdf

http://www.redlineoil.com/content/files/tech/ATF PDS 1-10.pdf

you can see that there is a difference. It "looks" like ATF might be a multi-grade type fluid while the PS fluid is a straight weight fluid.



Do a search on my remarks about PSF in this Topic. To summarize, the Redline PSF IHMO is only suitable for Honda PS. The newer GM PS and the Amsoil PS fluids are better suited for general use.

You are indeed lucky if your vehicle allows ATF as a suitable replacement.

 

[artificialist]

My Mitsubishi has a weird requirement that adds fuel to the fire of this debate. The manual calls for Mitsubishi PSF, OR Dexron type ATF.

 

[tommygunn]

Hah, all I know is ATF in general is a good, low-temperature low-wear hydraulic fluid...I think its a smart upgrade versus PSF myself.

Besides power steering specific fluid seems to have its "niche" and costs more anyhow, so quality ATF seems like a bonus to me.

Especially ATF+4 since its all GrpIII anyhow.

 

[Klutch9]

My Focus specifies Mercon V ATF for the power-steering system. That was easy

 

[widman]

A couple of days ago I posed this question to a formulator at a blending plant where both are made. This was his response about the power steering fluid:

This is basically a multigrade hydraulic fluid with seal swell additive.

The cheaper ones on the market are just base oil plus seal swell.

Regards,

 

[Garak]

Originally Posted By: MolaKule
You are indeed lucky if your vehicle allows ATF as a suitable replacement.


Nissan/Infiniti does it in a strange way. The manual recommends Genuine Nissan PSF only, if you're in the States. If one is in Canada, one can use the PSF or Dexron VI. I assume the theory is that Dexron VI is better in the cold.