Depending on the model of fan, you can pull them apart and replace the liquid inside I believe, havn't done it, dunno what its called, but you can get it from Toyota,
makes it like new again, I'm not keen on electric fans, where you are you need good airflow most of the time eh, you will need two vials I am told. I'm sure someone on here has done it and may be able to throw more light on the subject cheers.