Power steering fluids and viscosity indices (1 Viewer)

[nukegoat]

So theres always anecdotal discussion around atf vs hydraulic fluid vs power steering fluid... and most people fall into one camp or another ideologically but without much discussion on the engineering IMO. In researching this topic myself, i have a theory on why toyota may have suggested atf instead of hydraulic fluid - the viscosity index of atf is more like a multi grade oil rather than a single weight. In short, it is relatively thinner when cold and relatively thicker when hot compared to straight iso32 oil.

In looking at the astm testing method, atf is often in the 170 - 180s for v.i. whereas the beloved dte24 is around 100 v.i. (higher is "better")

Given the wide heat range the pump deals with, it may be reasonable to assume that a multigrade fluid is safer for all temp ranges?

Thoughts?

 

[Brimley]

Beats me. But I didn't know Mr. T recommended ATF so thanks for the info,

 

[nukegoat]

Beats me. But I didn't know Mr. T recommended ATF so thanks for the info,

This is the blind ideological camp. But for what its worth the cap states dexron ii/iii

 

[CJF]

I think it's because it's more universal and readily available, so better matched to third-world conditions.

Same reason the washer fluid reservoir has a screen, gas tank has a pre-filter, air cleaner has a tuna-can debris catcher, etc.

 

[CJF]

...

 

[Fj81]

Oh sorry, it was one of your threads so I figured the answer would have to do with head gaskets.. carry on.

 

[cruisermatt]

@nukegoat thanks for bringing this up. I was actually just thinking about the same thing the other day, I have a GM pump (which GM wants “power steering” fluid in), the Toyota steering box (80 series, Toyota wants ATF there), and GM hydroboost. I figure I should do what’s best for the pump and that the steering box and hydroboost are less picky due to not spinning at hundreds or thousands of RPMs... just guessing though.

 

[Hornd]

The pump has a direct connection to the motor thru the gear. If pump fails and tranny fluid goes into motor no major issue.
Do not overthink this a Toyota Engineer already looked at the 10,000 best things to use and came up with ATF. A Qt of Synthetic ATF gets it done and was $5 and change.

How do your Dizzy, Crank, and Oil Pump gasket look?

 

[LC4LIFE]

It's simple for me, especially after seeing so many of these rigs at the 200K+ mark running the Toyota recommended atf in the power steering with no issue. I am sticking with what they recommend, atf. I would say, like much of the other fluid discussions on this forum, that keeping it cool and clean is key, not necessarily the type.

 

[nukegoat]

@nukegoat thanks for bringing this up. I was actually just thinking about the same thing the other day, I have a GM pump (which GM wants “power steering” fluid in), the Toyota steering box (80 series, Toyota wants ATF there), and GM hydroboost. I figure I should do what’s best for the pump and that the steering box and hydroboost are less picky due to not spinning at hundreds or thousands of RPMs... just guessing though.

Yes - the vane pump generates the heat and pressure etc

 

[Red Merle]

the viscosity index

The hwaht index?

OK, so real time, I run ATF in my rig which is garaged but will spend nights out in the wild in -25 F on a fairly regular basis for 5 months out of a year. Today was +98 with the heat index and it was easily that in my garage and hotter in the driveway.

Which would be better? I have a slight leak using the ATF and swapping it out is a breeze.

Give us the pro jock analysis on what those numbers mean to you.

 

[Red Merle]

The pump has a direct connection to the motor thru the gear. If pump fails and tranny fluid goes into motor no major issue.
Do not overthink this a Toyota Engineer already looked at the 10,000 best things to use and came up with ATF. A Qt of Synthetic ATF gets it done and was $5 and change.

How do your Dizzy, Crank, and Oil Pump gasket look?

And a good day to you, sir!

Haven't seen you in a while, but this is the type of hard hitting decision making that I feel we lack at times.

 

[thatcabledude]

@nukegoat thanks for bringing this up. I was actually just thinking about the same thing the other day, I have a GM pump (which GM wants “power steering” fluid in), the Toyota steering box (80 series, Toyota wants ATF there), and GM hydroboost. I figure I should do what’s best for the pump and that the steering box and hydroboost are less picky due to not spinning at hundreds or thousands of RPMs... just guessing though.

I use trans fluid in mine.

 

[Red Merle]

I use trans fluid in mine.

This should be a poll.

 

[nukegoat]

Ironically power steering fluid is also a high viscosity index fluid

 

[maxamillion2345]

I don’t have a toyota pump anymore, I have a PSC ‘P pump’ now, but I do have a toyota steering box and tapped for hydro assist.

Howe and PSC both specify only AC Delco ps fluid regardless of style/series pump. Looking around you’ll find a lot of people swear that this fluid stopped their cavitation issues. I know on my buddies crawler with full hydro a high output TC pump he had a ton of groaning and whining that would not bleed out, he put foam in the reservoir and a few other things and swapping to the ac delco fluid eliminated all cavitation.

Ancedotal and ideological maybe and not neccessarily a concern of stock rigs but its good stuff and any Toyota pump and gear box would be fine running it. Then again stock stuff runs fine on cheap cheap ATF so...

I will add that I’m a firm beleive you can feed these stock steering systems any lightweight oil (ps, atf, various similar weights of hyd) and they run just fine.

 

[-Spike-]

It's simple for me, especially after seeing so many of these rigs at the 200K+ mark running the Toyota recommended atf in the power steering with no issue. I am sticking with what they recommend, atf.

Let me confuse you then- it's been said that Toyota fills the system with PSF, and only recommends ATF for topping off.

I would say, like much of the other fluid discussions on this forum, that keeping it cool and clean is key, not necessarily the type.

I'd agree with that. If there's any downside to using either fluid, it's practically immeasurable in application.

 

[LC4LIFE]

Let me confuse you then- it's been said that Toyota fills the system with PSF, and only recommends ATF for topping off.

Unclear for sure. From what I am seeing the FSM says to us PSF during rebuilding or servicing the pump, but calls out Dexron II or III for fluid capacity and type.

 

[Red Merle]

Nobody knows. Run whatever. Done

Keep it full.

 

[Red Merle]

This is the blind ideological camp. But for what its worth the cap states dexron ii/iii

This is a fair point. That isn't really the camp that I want to end up in, but if I have to choose between giving it up for a greener pasture that might not be all that green and a known mistress like Miss Dex. I don't know? Do I? Meh, not really, but I also don't want to run out of ATF at somepoint and it would be nice to know how to keep a 1FZ-FE humming along on a mixture of bee pollen, good intentions, farm rated ATF, motor oil, and maybe some hemp oil now that WI can grow that legally. I am pretty it would be happy just to have you dumping stuff into it occasionally and figuring it out as you went. She's not much of a complainer, really.