Though it might seem like a wacky concept, it is possible to filter used oil through layers of denim to purify it. The easiest way to create a denim filter is to take your used oil and put it in a container with drain nozzle. Then cover the drain nozzle with two to three layers of denim, and drain it into another container through a funnel. The process takes quite a while to filter the used oil.
The filtered oil can be recycled for use in the same engine after being filtered through the denim, though this isn’t recommended for certain engines. I tried it out on my outboard motor using recycled Yamalube 2S oil, and it seemed to work. The quality of the filtered oil was quite good for being filtered through a household item.