Well, I think where you use the car does have some influence on what weight oil you might use.
Also, I found that since using a electric oil extraction pump, I can easily change the oil to the grade best suited for the upcoming two or three months.
For instance, the weather in Chicago was fairly warm until January. Certainly not sub-zero. I left the 10W-40 in until I saw the weather reports of upcoming sub-zero nights.
I changed the oil and filter to 5W-30 Castrol GTX to help with this cold snap that lasted about a month.
Once the snap was over, I went back to 10W-40 GTX and a new filter.
Probably too much for some owners to deal with, but I actually enjoy it now since the electric pump makes it easy.
Aside from weights, change hot and often. If you use a major brand and do this, you are fine.