I have just purchased a 2007 Acura MDX with 85,000 on it and want to change out all the 4 wheel drive fluids because it's not clear when they were last done. This car originally came with Honda Z1 transmission fluid in the rear differential as well as the transmission. However, Honda/Acura doesn't make Z1 anymore and the Acura recommendation now is to use Acura "all wheel drive" fluid in the rear differential and to use their new DW1 fluid in the transmission. Confusingly, both Amsoil and Redline now recommend a transmission fluid or fluids for use in the transmission in the '07 MDX, but make no recommendation for the rear differential because apparently they don't think any of their fluids is an exact or close enough replacement for the all wheel drive fluid. It seems to me that if their fluids were suitable to replace Z1, which was originally in the differential to start with, they should still be suitable now to use in the differential. Acura wants you to replace that fluid every 15k so I really want to use a high quality synthetic in both the transmission and differential so I won't need to replace it nearly that often. Do you guys believe that the Redline D4 and/or Amsoil tranny fluid would be safe to use in the rear differential or should I stick with the OEM all wheel drive fluid? My goal is trans and differential longevity as well as optimum fuel economy. As always, all thoughts will be much appreciated.