Olive oil, canola (extracted from rape seeds), sunflower oil, and corn oil are good and healthy at normal temperatures. However, when they are heated, they turn out to be unhealthy. Hence, they are not suitable for frying purposes.
Reusing the oil which was already used for frying once generate toxic substances which increase the fat deposits in the heart veins. So, please do not reuse the oil used for frying once – throw it out!
Coconut oil & palm oil are well-suited for frying purposes. These oils can be reused after frying also. There are no harms by recycling.