So I have a ZF p/s system that takes ATF, I've been flushing it with a baster 10oz a time every 20-50 miles for a while now, I'm on the seventh quart of fresh ATF now. I have used Valv, ST, and Castrol all dexIII/merc universal. I have noticed that all 3 of the brands Ive used are notably different in thickness at room temp when you shake them and make my steering feel differently (heavier or lighter) as I add 1+ quarts of a certain brand to the system. The full system is just shy of 2 qts capacity for reference if the net is right. So far I like the feel of the Castrol which in my shake feel is the middle in thickness with Valv being heaviest and ST being thinnish, 2.5qts if Castrol cycled in now back to back. I am going to fully drain the system and address the OEM hose clamp leaks I have then refill with probably Castrol. I'm wondering what others run in their BMW PS system to get the best effect. The system says Dex3, but 1992 was a long time ago and fluids have changed a lot... what should I run in my P/s for ATF? The internet has tons of conflicting info on the subject and I know there is good feedback to be had here so I was hoping to get a more concrete answer.
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