I have a 2000 F150. There are about 90,000 miles on it. The power steering fluid has never been changed. My question is, instead of trying to do a full flush, could I just replace what is in the reservoir? It should mix in eventually and replenish what is there right? Trying to avoid crawling around since I am now old AF. Also I might only put 20-30k more mile son this truck. Just keeping it limping to the end.

 

That is what I would do. I have a hand held mityvac that is very useful in sucking out fluid. You could do it more than once over a period of time to get most of the old fluid out. This reminds me that my 02 still has the original fluid in it.

 

Do not use power steering fluid. Use Mercon V spec ATF. I use a turkey baster to suck the fluid out of the reservoir.

 

I think the manual for our old trucks specifies Type F trans fluid doesn't it?

 

Nope, it specifies Mercon, which is superseded by Mercon V. Type F hasn't been used since the 1970's. I use Mobil 1 universal synthetic in my power steering.

 

> "could I just replace what is in the reservoir?"

Yup. 2 ideas...
- When I do this, I find a bit of seal rejuvenator, or a fluid w some in it.
- You bought a qt??? So, use it.
Suck and replace, once.
Run the truck for only 30 seconds or so, so the new fluid travels, but doesn't mix very much. (No sweat if you go past 30, but...) Now kill the engine and suck & replace & repeat, until your qt is almost gone. (I carry a milk crate w bits of each fluid, & some water, w the jumpers, etc.)
IIRC these take 2+ qts, almost 3(???) So this way, you have replaced a larger % of the fluid. Not just a super "top-off.* (Hey, the tools are out. That baster will never see another turkey. Spend 5 more min.)
This is a partial substitute for crawling under to loosen a hose and make a mess. (I am almost OAF, too. &#128518 You could do this annually for a year or two if the fluid is V old and you can afford to blow a qt. Remember, 30,000 (IIRC) for the ATF, also. But, that's usually a crawl under. Just replace what drains, or, again, use a drain replace drain replace method. I do this mainly when I KNOW a vehicle MAY have not been maintained.

 

Do not use power steering fluid. Use ATF. You can add a seal additive, but again, do not use "power steering fluid".