Volvo Repair: What to do to make my car run better in the snow, winter tires, oil treatments

Question
I have two Questions. 1) What can I do to help my car drive better in the snow. I down right sucks when it snows. I live in the Northeast and use my Volvo for my job where I drive alot into different areas of the state. I have tried to put weight in the back and it really doesn't help.
2) My car has well over 250,000 mls on her and I was wondering if you believe in adding any oil treatments to the oil. I was wondering if they help or hurt the car.  

Answer
just use good oil not cheap oil  use original oil filter   due the oil chnages on time and that's it oil treatment  just  cost more money   you dont get much  from it use thiner oil in colder weather  like 0-30w 5-30w   and in summer 10 -w30 or 15 w-30 . get a cheap set of winter tires.you only use them 3 months so they last you years