Red Line D4 ATF in a 4EAT

[stevenva]

I'm going to be changing over the ATF fluid. I'm not going to flush it. 2 or 3 drain & fills spaced a little apart. Filter will be changed on the last one.

Any mileage improvements on going to full synthetic?

Any issue with mixing Amsoil ATF with Red Line D4? (I have almost a gallon of the Amsoil left over from another project)

[Kennyfvholla]

If I'm completely honest, stick with the fluid that Subaru sells at the dealer. Fill it with what's always been put in the transmission.