PSF vs ATF

[Torox]

2013 Chevy Express 3500, 170k miles.

I’m putting in a brand new GM power steering pump, all new lines, a filter, and I already installed the brand new GM hydroboost. There is much debate around using PSF or ATF. My GM manual says to use PSF. I bought a gallon of Napa PSF because I’m going to flush the entire system. I’ve mostly worked on older cars where using ATF didn’t matter but I’ve been told that on newer cars, I should use what the manual recommends. That being said, is there any upside to using ATF or any downside to using PSF? Would a better-quality ATF be better than Napa PSF? I want to use whatever is going to be best for protecting and prolonging the components in my van within a reasonable cost.

 

[Chris142]

Several years ago I put ATF in my Jeep's power steering that said to use PSF. The pump growled and whined for 3 days at which I swapped the ATF for Ps fluid.

 

[nascarnation]

One of our experts should weigh in, but basically they are typically 0W20 fluids with different additives. I think PSF would not be good in an automatic transmission, but a good ATF is fine in power steering. I'm curious as to what failed in your system?

 

[tig1]

I have used M1 Mercon V ATF in my PS pumps for 30+ years and to date have not had one fail. Perhaps 1 million miles or more.

 

[Torox]

One of our experts should weigh in, but basically they are typically 0W20 fluids with different additives. I think PSF would not be good in an automatic transmission, but a good ATF is fine in power steering. I'm curious as to what failed in your system?

PS pump was leaking out of every possible point. The hydroboost was leaking into the cabin. The lines are 7yrs/170k miles old. I got an ACDelco reman thinking it would be quality, turns out it was not (see my other thread). So I ordered a brand new pump and lines. I just want to do this with quality fluid and not have to even think about it for another 5 years.

 

[Torox]

I have used M1 Mercon V ATF in my PS pumps for 30+ years and to date have not had one fail. Perhaps 1 million miles or more.

I’ve always done the same, but they were older cars. This is only a 2013 but the manual calls for PSF and models just a few years newer call for ATF, so it makes me think there’s a reason why this one wants PSF.

 

[JMJNet]

I have a 95 Suburban with 6.5L Diesel, I have put both type, PSF and ATF.
It does not have any effect.
Mine was spec for PSF.

The reason for ATF was at one time during a long distance trip, one of the fitting let loose and leak.
The only available fluid was ATF Dex III.
That was 8 years ago and I have not replaced/flushed it yet.
It is still running.

Just my experience, yours may be different.

What have you been using this far?

 

[92saturnsl2]

Either will probably work fine, but I'd use the PSF per the manual. I replaced all the PS lines in my Grand Prix recently and was faced with the same dilemma. The manual calls out PSF with a GM part number. I picked up a bottle of Rural King PSF, which had that part number listed as compatible on the bottle. Cost about $3 and has worked great since.

I learned an expensive lesson about 15 years ago to stay with the OEM recommendation for PS fluid. I had a 2001 Jetta and when I first bought it (it was a couple years old) I checked all the fluids and topped up the power steering with ordinary PSF. Little did I know, the OEM used some expensive synthetic Pentosin stuff from the factory and the two fluids combined to form a horrible milk-shake like substance and trashed the power steering rack in quick order.

That said, I've substituted ATF for PSF in older cars before with no issues, but I'd be very leery in doing this on any modern vehicle. I suspect the PSF has specific additives for steering systems that ATF (being a transmission fluid) lacks.

 

[Torox]

I have a 95 Suburban with 6.5L Diesel, I have put both type, PSF and ATF.
It does not have any effect.
Mine was spec for PSF.

The reason for ATF was at one time during a long distance trip, one of the fitting let loose and leak.
The only available fluid was ATF Dex III.
That was 8 years ago and I have not replaced/flushed it yet.
It is still running.

Just my experience, yours may be different.

What have you been using this far?

It had a mix of PSF and ATF in it but it was very dirty/burnt. I’ll be doing a thorough flush and installing a filter with the new components.

 

[Snagglefoot]

I also have the Chevy hydroboost system on a 2008 3/4 ton. It had nothing but AC Delco power steering fluid and I turkey baste the pump volume about once per year and replace it with more AC Delco fluid. The system now has 200,000 miles. I plan to replace the pump as it leaks in cold winter weather. I have more AC Delco fluid to put into the replaced pump. There are numerous answers because numerous fluids will work. I use Mercon V in my Ford Taurus.

 

[Jetsfan421]

I use atf+4 in my kia's power steering. As a synthetic fluid I believe it to be an upgrade over the original spec psf3 and it's alternative dexron 2. Similar specs but with superior shear stability and cold flow properties.

 

[tig1]

I’ve always done the same, but they were older cars. This is only a 2013 but the manual calls for PSF and models just a few years newer call for ATF, so it makes me think there’s a reason why this one wants PSF.

I wouldn't be concerned about that.

 

[BlakeB]

I put a new PS pump in a 2004 GMC 2500HD in April of this year after the shaft broke off inside the PS pump. I also dropped the trans pan and changed the ATF and filter while it was on the lift. I used Delo Syn ATF HD ( TES-295 clone) in both the PS/hydroboost system and the transmission. No issues with either so far and I don’t expect there to be any. The truck showed 94,341 miles when I replaced the PS pump and it has accumulated more than 1,000 miles since the swap.
I did use a brand new OEM PS pump, and a new aftermarket pulley. I didn’t bother with trying to pull the old pulley off and reuse it, the aftermarket pulley was only $18.

True mileage on the truck is unknown. The truck was purchased from a Chevrolet dealer in 2010 showing 52k miles, but we later found a note in the owners manual that the instrument cluster was replaced at 56k miles. The truck potentially had 108k miles when it was purchased with “52k miles”.

 

[Torox]

Thanks everyone for your feedback. I think I’m going to go with PSF. I just can’t find any solid scientific reason or advantage to using ATF. There are equal amounts of anecdotal pros and cons to using ATF and equal amounts of anecdotal warnings against it. That being said, I’m just going to play it safe and go with what the manufacturer recommends, which is PSF (GM 89021184).

I currently live in the hot South but am soon moving up North and will be there for the winter. I may be in one or more areas of Ohio, Chicago, Wisconsin, Maine. It gets super cold in some places and I’ve read about having issues with PSF getting too viscous to flow and causing damage in the pump or lines. There are cold climate PSF’s available - should I get one to be safe? If I use one, will it still work well in hot temps if I return to the South at some point?

Should I use a synthetic PSF over a conventional PSF? I’ve read good things about Amsoil, is it really a superior product or is it more purported snake oil like Lucas? Any recommendations for good-quality PSF?

 

[ARCOgraphite]

Is not PSF = Dexron/Mercon?

I'll tell you, the automotive and lubricant industry is pretty bad properly specifying and labeling products in this area - Just like modern Coolant choice is so confusing. SIlicate free, OAT, HOAT, P-HOAT ... Jeepers!

Forget synthetic. PS/ATF fluids are typically using low boiling point naphthenic oils. And they are fine and have good attributes for their purpose. Just NOT in an engine crankcase.

 

[Torox]

Is not PSF = Dexron/Mercon?

I always thought it was but people seem to be pretty evenly divided on this. A lot of people quote technical data on both but still disagree.

Forget synthetic. PS/ATF fluids are typically using low boiling point naphthenic oils. And they are fine and have good attributes for their purpose. Just NOT in an engine crankcase.

I’m not putting PS/ATF in the engine, only the power steering system. I considered synthetic because it appears to do better in cold climates.

 

[JMJNet]

I don't think the choice matters.
IMO, it is more important to flush the P/S fluid every few years than the choice of fluid.
Yes, they do get burn and it caused trouble.

 

[dfarr67]

GM has some cold climate psf- semi synthetic I think.

 

[Torox]

GM has some cold climate psf- semi synthetic I think.

I wanted to use that. I ended up using Royal Purple Max EZ synthetic. I replaced the PS pump, all the lines, cooler, and hydroboost. I did a full flush and added a filter. Hopefully I won’t have to mess with it again for a long time.