Hey guys. I found a cross-reference chart for the Mobil424 oil we need in the rear end of our Prairie 650s. I'll give you the link so you can go to the site yourself, but I'll post all of the oils they cross to also. It's an Australian site so some of these oils I've never heard of!! Anyways, here goes.
Mobil------Mobilfluid 423 or 424
Castrol----Agricastrol AS or TFD
Caltrex----RPM Tractor Hyd Fluid
Shell------Donax TT or Donax TD
Hope this helps if you are having trouble finding the Mobil424.