Here's the situation:
- temperatures here range from 40-5F
- I ride once a week
- I park outdoors
- I top off the tank after each ride
do i really need to add stabil?
No!
Cookie
No
If you are concerned, it can't hurt to add it.
I would think if you are going to let it sit for a month, you would be best off with it in there. Since you ride only once a week, taking two or three weeks off due to weather or whatever might result in it sitting longer than expected, so why not add it just in case?