Best ATF to use in Power Steering system.

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Feb 25, 2009
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What's best in for long term durability of the seals and hoses in a PS system? DexMerc III/Mercon V/Full synthetic??? I don't use regular PS stuff ever since two different mechanics said ATF is actually better than regular PS fluid. Ends up being cheaper too if you're doing a drain and fill of the tranny anyway I would think.
 
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What's best in for long term durability of the seals and hoses in a PS system? DexMerc III/Mercon V/Full synthetic??? I don't use regular PS stuff ever since two different mechanics said ATF is actually better than regular PS fluid. Ends up being cheaper too if you're doing a drain and fill of the tranny anyway I would think.
The owner's manual for my Ford 1994 F150 calls for Ford Type F transmission fluid to be used in the power steering system. Type F is still readily available at some auto parts stores.
 
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You aren't dealing with friction materials or combustion materials so it doesn't matter. It acts as a hydraulic fluid so you can use almost anything. You could use motor oil if you wanted to.

Biggest thing would be making sure the fluids don't contradict eachother.
 
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Lots of euro cars use hydraulic fluid'

pentosin.jpg
 
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The owner's manual for my Ford 1994 F150 calls for Ford Type F transmission fluid to be used in the power steering system. Type F is still readily available at some auto parts stores.

It probably left the factory with Mercon.

Of the Ford vehicles I've owned that specified Type F, I used Mercon instead of Type F. Never a problem and never a bottle of obsolete fluid useless for anything else laying around.
 
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Clean and meets OE requirements is how I feel. I used MaxLife/M1/Red Line D4 ATF for the ATF systems and the specific fluid for everything else.
 
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I have often wondered why TMC spects Type I-IV for my ATF but Dexron 2/3 for the power steering. Of course, if you have ever looked a the OEM shop manual gibberish for my 04, you will get some insight into this conundrum.
 
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I use Dex VI in any of my GM vehicles. I was told by a Mobil engineer about 15 yrs ago that trans and PS fluid are essentially the same thing and whatever differences existed were so minor that it didnt matter. When I switched my POS 05 Duramax to synthetic to compensate for the wimpy pump the Dex VI was about 1/10 of the price of synthetic PS fluid.
We actually had a truck at work with super singles on the front that called for 15W40 diesel engine oil
Take that for whatever you want, some random guy on the internet etc etc.
 
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The last few revisions of Dexron III (maybe III (H))had tests for power steering systems.

Does anyone know if Dexron VI has the same requirements?

I've assumed that is why Toyota wanted Dex III in their power steering systems, rather than T-IV or WS.
 
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Jan 20, 2013
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As far as I know, GM has always specified a dedicated PS fluid and not ATF in their PS systems. Despite the apparent interchangeability, I use PS fluid where recommended to assist in future fluid identification.
 
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