The thermostat may in fact keep the temp close to the thermostat sensor quite constant but there are usually large temperature gradients in a fridge. Place your thermometer very close to the sensor and I bet it keeps quit constant temperature. If you want the entire fridge to follow that constant temp. , install a very small fan to circulate the air inside. However, it is most energy efficient to store things that need lower temps, (like fish and meat) near the bottom and store things that require only about 55F, near the top. Don't store condiments like mustard, ketchup, etc. in a fridge. They don't need refrigeration if they get used up in less than six months. Eggs, if coated with oil when purchased, also don't need to be in the fridge. For proper use of a fridge the thermostat should be placed near the bottom set for about 40F. Then the top of the box will be ~50F and will vary with outside temp. -- Richard P