My User's Manual suggest to use GL-5 Gear Oil for the differential.
- 80W if operate below 0 degree
- 90W if operate above 0 degree

Can I use Valvoline DuraBlend 85W-140?

 

no, It would be to "heavy" of a lubricant. I know castrol and valvoline make 80W90 and Mobil 1 makes 75W90. 85w140 means 85W when cold or winter, and 140 for when it is hot. The larger the viscosity range the less lubricant in the same volume of lubricant. To make it go from 85 to 140 additives are in the oil, these addiditives do not add any lubricating properties. A single weight oil such as 80w or 90W will be superior because it is nothing but oil. Imagine a ball of spagetti. when it is cold the ball is bunched up, whe it gets warm in spreads out making the oil thicker that is how I understand additives work.