I think it depends more on how much stuff you have in it, how much you open it, and how warm it is outside. I used to keep mine at 5 and I remember opening a coke can one time from the top shelf of the refrigerator only to find it was a little slushy, and that was with a full refrigerator. I'd say outside temps were around 30-45 because that was early October.
2007 T-286SR Cherry/Granola, #6236, original owner, current mileage: 9467.8 (as of 5/26/19)
1997 T-2653 Blue Denim, #5471
1979 12 1/2' MC, Beige & Avocado, #4639
Past Sunlines: '97 T-2653 #5089, '94 T-2251, '86 T-1550, '94 T-2363, '98 T-270SR