Storing Deep Fryer Oil
If you strain the oil using a coffee filter inside a funnel, it will catch even the tiny bits that would slip through a wire strainer, making your oil super-clean. Store in the refrigerator, ideally in a glass bottle or jar, and it will keep for at least six months. I haven't stored it undisturbed for longer than that, so I can't speak to how well it keeps past that point. If you use and then re-filter the oil, you can start the six-month count over. I have only repeated this twice, so again, I can't speak to how the oil keeps when you do this many times.

One more item: I don't know if it matters, but I use grapeseed oil. I would assume that this also works for other frying/deep-frying oils, but I can't say for sure.