I'd had good luck with the Valvolene sythetic power steering fluid; put it in at 50K, did one turkey baster fluid change at 85K and things are still smooth and quiet at 101K.
Cheers, SocksE420

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SocksE420
97 SL500 74K
96 C280 110K(SOLD)
96 E320 111K(SOLD)
95 E420 107K(SOLD)
88 300TE 142K(SOLD)
77 300 D 144K(SOLD)