Apologies for the zombie thread but I figured after finding it with a brief search, no reason to begin a new one if a perfectly relevant one exists. I'm also looking at doing a fluid service for a GM 89021184 application. Looks like there are a couple options out there these days, is anything equal or better than the GM fluid? Looking at the following options which I readily found:
1. GM 89021184 $12 for 16oz on amazon
2. AMSOIL power steering fluidCN $9 for 16oz MSRP
3. Preston PSF $6/qt
4. Preston Full Synthetic American PSF $14/12oz on amazon
5. Various house brands PSF
Not sure how much these fluids really vary, might just see what the local Amsoil dealer is selling their stuff. I also saw some Valvoline MaxLife Power Steering Fluid on a local retailer's website, but can't find it listed anywhere else on the web so I'm not sure its still actually produced.