Last year, when changing out my fork oil, I tried the ATF option, and HATED it. Don't remember what brand, nor for sure did I know exactly what it's viscosity was, but I hated it. Totally wrong handling characteristics when I went down the road. I ended up buying regular 10w fork oil and replacing the ATF after only a month or so. I still have the OEM springs and run 10psi in them.