A question on cooling/refrigeration (details inside)

Food safety guidelines call “freezing” storage at 0 degrees Fahrenheit, and I’m pretty sure refrigeration is storage at 40 degrees Fahrenheit.

That freezer is likely colder to mitigate temperature changes caused by opening the doors.

Energy. Once it’s frozen (-4) , it’s a waste of energy on the compressor to keep things any colder.

As for why -4 and not 13 above, I have no idea.

There are sound reasons for maintaining frozen food at temperatures far below the freezing point of water. The primary reason being that there are substances in food (salt and sugar for example) that considerably lower the freezing point. There are also hearty pathogens that employ some of those substances to thrive and multiply happily in what may appear to be be a frigid environment.

-4 (freezer) and 38 (refrigerator) temps are just the factory-set defaults. You can change them if you want, but you should not change them by much, for reasons that @stanleybmanly and @Seek_Kolinahr mentioned. A good test for the freezer is ice cream. Set the freezer for the way you like your ice cream. @elbanditoroso At -4 you may find that your ice cream is frozen too hard, but at 13 it will probably be too soft.

We have set our freezer temp at 2 degrees F, and our fridge at 38. Our fridge also has a “deli” drawer that we can set at a different temperature from the rest of the fridge and we like it at 34. You want your fridge temp to be as cold as possible without causing your fresh veggies to freeze. We found that lettuce begins to freeze at 36.