I am not sure that will actually safe you money.
Running the numbers, the average fridge should cost you about $5 per month to run (calculating with european electricity cost which is higher than the US).
Therefore, shutting it down for 4 days will probably "safe" you around a buck in electricity.
That doesn't take into account that it will get to room temperature and that you will have to use additional energy to get it back to its usual coolness. There go your savings.
I turned my fridge of when I left for 3 months, that was definitely worth it. For 4 days, I don't think you gain anything.
1. "Save," not "safe."
2. The amount of energy used by any refrigeration system is, in general, proportional to the
difference in temperature it is attempting to maintain and the amount of time the machine is trying to maintain that difference. In almost all cases, allowing the conditioned space to heat up (or cool down) to ambient temperature and then cooling it down (or heating it up) again later will be more efficient than keeping it conditioned all the time.
3. However, you're right that 4 days is not a lot of time. Although I don't think the savings will be zero, they might be negligible -- especially if you have to make an extra effort (e.g. eat more food than usual) to clear it out.
Note that this sort of reasoning applies to all heating/cooling appliances, not just the fridge. When I go out of town I turn my tank water heater to the "vacation" setting (I don't turn it "off" because then I'd have to re-light the pilot) and set my programmable thermostat to either as low or as high as the house can stand without pipes freezing or excessive humidity causing mold, respectively depending on the season.
I also [try to remember to] shut off the water valves to the dishwasher and washing machine, but that's more about avoiding burst flexible hoses and flooding rather than saving energy.