I use my wok for those few occassions for deep frying, and I usually discard the oil afterwards. I use grapeseed oil. The wok's not too deep, so I don't use more than a cup or so.
Others who do this often may have special fryers, etc.
..and a question: can you safely save used oil? I suppose it also depends what has been fried? How is it stored?
Nathan's deepfried artichokes in 'EVOO' prompted this question. (Holy Cow! if that's a big pot, them's an expensive batch of 'chokes!)
I'd love to hear from you all.