Well, seeing that winter is(slowly) decending upon us here in Calgary I'm thinking about my fluid wieghts. Trying to put as little wear on my engine, tranny and diffs as possible.

Not such a big deal when I'm in the city, my truck stays in it's nice garage. But when I go out to the farm it sits in the cold, without a being plugged in, or sheltered(-30 -> 5C)

I'm planning to go with 0W30 for my next oil change, but how low can I go for diffs and tranny? I'm running 80W90(pretty sure) now, but how low can I go? 60W90, 50W90?

 

A 75W90 synthetic oil would work well in the axles. You can run something like Redline MTL in the tranny and t-case, 70W80, it is as thin and auto tranny fluid:
- http://www.4crawler.com/4x4/index.sh...ntheticGearOil