which mineral oil ?
 

My power steering is making noise and the mineral oil level is at the bottom of the tank. Which oil to use ? Oreilly Autoparts gave ATF1 automatic transmission oil which is fully Synthetic pentosin oil for 18 bucks a liter including tax. It's not correct is it?

It's not correct, but the correct fluid is by Pentosin.

What year is the car you are working on?

2001 AR

I bought CHF 11s and poured in half the can and the noise is now gone. 23.99 dollars including tax from NAPA auto parts.

Cool. That's the correct stuff. You can also use CHF 202 which is their newer product, less money and miscible w/CHF 11S.

NEVER use anything but the correct fluid in an Audi or VW! You will end up replacing the majority of your system. The steering rack is more than a grand, plus labor, plus the pump and labor. Can be way more than $2500 for a simple mistake. I've learned the hard way on one of my VW's.

+1 on CHF 202

i had to have the steering rack in mine rebuilt due to the wrong fluid being in there not long after i got it

like they say, do it right, or go home