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A few months ago I noticed that my power steering fluid was a little low. My owner's manual stated that automatic transmission fluid should be used, so I went out and bought a quart of cheap ATF and topped it off. It didn't occur to me until later that this could be a problem, when I was reading about issues with mixing fluids in a transmission.

I haven't had any problems, but I could have just been lucky. On the other hand, maybe the requirements for power steering are such that it won't make a difference. Is it really necessary to flush the whole system if fluid needs to be added, if you aren't sure what brand was in there to begin with?

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Most ATF based power steering systems are not especially picky about fluid quality. That is not to say that using the lowest quality is a wise choice. Not all systems use ATF and some would be damaged by it, so it is appropriate to check the manual and only use the correct fluid. Many system do not specify a change interval, suggesting that the fluid is expected to last the life of the vehicle.

Power system fluid level should not drop. When the fluid is low, a leak is probable. These should be located and repaired.

Automatic transmissions are a different story. The exact fluid specified must be used. The fluid is just much a "part" as a shaft or clutch.

  • Agreed. There aren't any wear parts in the power steering like there is in an automatic transmission (clutches/bands). In the power steering, it's looking for hydraulic pressure and lubrication properties for the most part. – Pᴀᴜʟsᴛᴇʀ2 Nov 24 '15 at 12:41
  • The level hasn't dropped in the last few months, so I don't think it's leaking. However, I'll continue to monitor this. – user505255 Nov 24 '15 at 20:33

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