Is it safe to put transmission fluid into the power steering reservoir?

Dear Car Talk

Dear Car Talk | Mar 01, 1995

Dear Tom and Ray:

My neighbor, Mike, and I are backyard mechanics. Mike has forgotten more about automobiles than I will ever know! Mike says that you can use automatic transmission fluid (ATF) in your power steering system. I say that only applies to older cars. Who is right and who is wrong?

TOM: Well, you're wrong about one thing, Bryan....that Mike has forgotten more about automobiles than you'll ever know. Because you're right about the fluids.

RAY: It used to be OK to put automatic transmission fluid into your power steering reservoir. But it's not anymore. About 10 or 15 years ago, ATF started getting more complex. And now it has ingredients that are not recommended for your power steering system.

TOM: More importantly, you should never use power steering fluid in your automatic transmission. That's as bad as putting Paul Newman's salad dressing in there (nothing against the dressing, tastes great on my Radicchio!). But these days, ATF and power steering fluid serve two different purposes, and you need to keep the two separate.

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