Ok mates. While most of you in Australia are prepping for the summer season, here in Siberia I'm prepping for our extreme cold and long winter. Part of that means changing all the fluids and oils to a lighter weight and I'm a little confused as to what I need. Hopefully someone can give some input here on what I'm finding. I'm preparing for winter temps of -40C with brief moments dropping lower.

These are the numbers I'm finding in the manual and several online sources:

Engine oil - 5W-30 for operation in temperatures of +15C to -30C. Some sources say 5W-40. Any big difference between the two?

Manual Transmission Gear Oil - 75W-90 per the manual, but other say 75W-85

Front Diff - 80W-90 gear oil? Couldn't find a cold weather recommendation for this. One source seemed to indicate a 75W-90 would work, but not for temps above +10C

Rear Diff - LSD gear oil but which kind? Genuine Nissan or another?

Transfer Case - ATF DexIII fluid, not gear oil


Can anyone comment on these selections or differences? Is there something I absolutely should not do when trying to go with a lighter weight oil for the winter? Anything would be helpful. Thanks, mates.