Are the ATF, Audi hydraulic oil, and Mobil 1 synthetic fully miscible with each other, or does one have to fully drain the system before switching fluid types?

Ed

> Date: Sun, 13 Feb 2011 22:08:39 -0500
> From: d23haynes57@HOTMAIL.COM
> Subject: Re: What power steering fluid to use?
> To: vanagon@GERRY.VANAGON.COM
> 
> All the Dexron fluids are basically the same viscosity. The later ones are
> performance-stability improvements and friction modifier characteristics.
> For power steering viscosity over temperature is the thing that matters
> most. It should be noted that VW changed the specification from ATF to the
> Audi special mineral oil to improve cold weather performance. As that stuff
> is excessively expensive I use the Mobil 1 synthetic ATF. Any of the
> synthetic ATF's will work fine even in winter as it does not thicken up like
> conventional fluids.
> 
> Dennis
> 
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> David M
> Sent: Sunday, February 13, 2011 3:32 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: What power steering fluid to use?
> 
> Manual says just "Dexron" but there are several types II, III and IV, also
> Mercon. Which to use?