I use the Rotella T6 5w-40 in my XR4145. It covers the whole temperature spectrum for Western NY and meets the specs in the manual. You may also want to look into a block heater for winter. When it gets really cold, it doesn't matter what weight of oil you are using, it thickens to some degree. Having the block somewhat warm will help eliminate any premature wear due to lack of oil flow at startup. You can start your tractor without one when it is cold, but it doesn't like it.
As far as clean fuel, I have seen the effects of crappy fuel: grey-ish, stinky exhaust smoke, early/repeated exhaust regen. There are many posts and comments about fuel quality with these new engines. I haven't seen anything official, but my experience agrees with the gentleman from LS.
Happy Tractoring!