Hey Scotty!
I’m replacing the power steering pump on my 2008 Lexus RX 350 (127,000 miles). I’m going OEM, so no worries there. 🙂
My question is about replacing the current fluid with either automatic transmission fluid, or power steering fluid. The manual says to use ATF DEXRON II or III fluid for the power steering (I think there’s an updated version now for that liquid, but I digress).
However, per a very respected Toyota Certified Master Technician on YouTube, he says to instead use actual power steering fluid for the power steering system instead of ATF, regardless of what the manual says. This makes sense to me since, well, power steering fluid should be used in power steering systems, and ATF should be used in transmissions.
I would just like your opinion here: power steering fluid, or automatic transmission fluid, for the power steering system on my car?
Thanks!
The manual says to use ATF DEXRON II or III fluid for the power steering (I think there’s an updated version now for that liquid, but I digress).
Use Dexron III (sometimes labeled Dex/Merc). The newer Dexron VI fluid is backward-compatible with automatic transmissions only, not power steering.
The newer Dexron VI fluid is backward-compatible with automatic transmissions only, not power steering.
Weird. Dex6 is made from higher quality oil and meets tougher performance requirements. You'd think it would be fine.
https://bobistheoilguy.com/forums/threads/is-dexron-vi-fully-backwards-compatable.91151/
"Dexron-VI is certified backwards compatible only in GM's Hydramatic transmissions. It is not backwards compatible in Allison transmissions, and may not be in transmissions of other brands that originally called for Dex-III or Dex-II. Licensed Dexron-III is still being made, only now the spec is called Allison TES-389. I'd fully trust all the unlicensed Dexron products made by any major outfit...Chevron, Mobil, etc."
It may be an issue that GM has not tested it in older power steering systems. So it's "not approved". That doesn't necessarily mean it won't work, but if it causes problems GM wipes their hands of it.
@chucktobias I don't usually consider "what some guy said in a forum" to be trusted source. Here are manufacturer recommendations for Nissan/Infiniti models with hydraulic power steering.
That would mean that Nissan tested it. GM has issued service bulletins stating to only use it in automatic transmissions. This thread references a bulletin stating not to use it in manual transmissions and transfer cases that specified earlier Dexron:
Dexron VI has undergone vane pump wear testing (both auto trans and hydraulic power steering use vane pumps)
and meets the 10mg loss limit specified by the test. Previous specifications (ie Dex III) were only certified to 15mg . Dex VI definitely has better shear stability than Dex III. In my opinion, Dex6 is an excellent PS fluid. Better than older fluids. In my research, I haven't heard anybody report problems from switching to Dex 6.
( ASTM D2882-00 https://webstore.ansi.org/standards/astm/astmd288200)
In a manual transmission and transfer case the fluid has to meet mechanical lubrication requirements (for gears, chains, etc.)
In a power steering system, it serves purely hydraulic purposes. Power steering is lubricated by grease.
Chances are it would be OK in power steering but I personally avoid upgrading to Dexron VI unless the manufacturer or GM has tested it and verified compatibility in a particular application. Then again I tend to be conservative and cautious when it comes to that kind of thing. (I still run Dex/Merc in my old vehicles.)
GM probably won't test it either, because it's not the optimal fluid for power steering. It's overkill. A quart of GM power steering fluid costs less than a quart of Dex 6.
My 2007 Infiniti m35x tells me to use ATF dexron on the pump of the reservoir. If you have power steering fluid then go ahead and use it, but you can also use the atf dexron. Just make sure the bottle has “dexron” on it.
