While you may want to throw away frying oil once used, it could be a costly mistake. Given its rising costs and the hassles of disposing it properly, you're better off reusing it.
However, it's important to reuse oil safely. First, let it cool so it's safe to touch, then strain it through cheesecloth to remove any debris that may burn up on its second use.
Once you've sealed the oil in a container, you can refrigerate it for up to three months, or until it clouds, foams, or assumes a strange odor, after which you should discard it.