The car will also run rough with heavier than normal oil weight in cold weather because the oil is not as fluid, i.e. 10w-40 vs 5w-30. It may also be that you need a tune up. I made the mistake when I was a teenager of putting 20w-50 racing oil in my car because the engine burned oil and I thought it would help--thinking racing was a good thing. No one ever told me that it was for track use only. So, in the winter when I fired it up, the 8 cylinder sounded like it was using only 2, very rough starting, and created a lot of unneeded wear on the engine.

I never have that problem in my 850 and we get some pretty cold days. I run what the manuel suggests.