Sometimes it depends on which year Audi you have, but I would say go with
the synthetic with any year that you have. ;-)
"All 1990 - on Audi models have come filled from the factory with the
synthetic CHF 11S Audi hydraulic fluid (G002000). Please Note: Never mix
generic hydraulic fluid or other fluid with the CHF 7.1 or CHF 11S Audi
hydraulic fluid (G002000). If you or someone else did, flush the Audi
hydraulic fluid as described below."
Now are you sure it is the P/S pump making the noise?
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