power steering fluid 91 sunbird

going to change the old original power steering fluid out.
Its doesnt leak but want to change the old stuff out.
question is what kind 2 use since everthing out there is
for modern or synthetic cars. 91 didnt come with synthetic
and dont want to use it. any suggestion will be apprecaiated.
thank you in advance...

Found what to use. after researching they still have non-snythic out there. Use a name brand like valoline or castrol. if it says for newer or modern cars or pours in sub-zero weather. that is a synthic. so dont
use those.