As far as I know it’s backward comparable. I used Dexron III in my GT4 when it should have had Dexron II in it. No issues at all. The only time you have to be careful is when you’ve got something like a Honda! Then you have to use there power steering and axle fluids as they are the only supplier. I found this out to my expense! having changed the fluid (That Millers oils suggested) I then had to take it all out again. Thankfully, the Honda stuff was a clear liquid and the other was a red...