I would assume the 85 is more shear stable performance for the X-fer case. I would imagine its same as 90 but with less VM. Depends on the below freezing performance - maybe the 75W85 flow MUCH better.. My Nissan hated the dealer installed HD 80W90 MOBIL
Just Valvoline or Pennzoil or Castrol or Supertech 75w90 in the rear would be fine.
I put supertech 75W90 in the wife's Crosstrek with a noisy rear and .... its not noisy now! I though the dealer didn't change it when last requested, but the fluid looked
new and no metal fuzz on the drain plug magnet.
Maybe just a fluke.
Originally Posted by Jimzz
Most 75w85 seems to be conventional while most 75w90 is synthetic now.
I would run the 75w90 myself.
Are you sure 75W-85 can be had in a conventional? My understanding of the recommendation of 75W-85 was to actually force people into a synthetic gear lube because there is still some conventional spec's 75W-90 out there.
That being said, I have used a synthetic 75W-90 in place of the 75W-85 gear oil call outs in all my Toyota's with no issue.
I use Amsoil Severe Gear 75w-110 in my Tahoe. I switched to it from 75w-90, before I joined here, because I figured it would help with the towing I do. I tow a 6,000 lbs load about 200 miles round trip twice a month. I'm not sure if it helps or not.