Frying oil usually ends up with gross gunk floating around in it, making it a poor candidate for re-using, but it turns out that there is a simple way to filter all that crap out. All you need is gelatin.
J. Kenji Lopez-Alt of The Food Lab breaks down how and why this technique works in the link below, but I’m going to go ahead and share this game-changing method with you. First, let your oil cool, so as not to burn your precious self. Pour some water into a pot and sprinkle with gelatin. (You’ll need half a cup of water and a teaspoon of powdered gelatin for every litre of oil you plan on clarifying.) Let the gelatin bloom for a few minutes and then bring the water to a simmer, stirring until the gelatin dissolves. Add the dissolved gelatin to your dirty, filthy oil and stir, stir, stir. Cover it all up and place in the fridge overnight. The oil will float to the top, leaving behind all sorts of burnt bits and gunk in a neat gelatin disk. Pour it off, discard the disk of doom that remains, and use your clarified oil to fry up something tasty.