Just a note....I believe the Mobil1 gear lubricant only comes in 75W-90. If you go to an Isuzu dealer and supply them with Mobil1, they might ask if the axle additive normally used with their own supplied fluid is needed, not sure about this one...but something you should know for sure if you're doing it yourself.

All fluid quantities are given in the Vehicross owners manual you should have for engine oil, axles, TOD and transmission...which doesn't seem to be recommended for change in the maintenance schedule except for excessive use.