From lifehacker

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 quart 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.

I think this could work for removing the junk from really bad oil. What you think?

 

I think I'd rather just change the oil...

 

Well sometimes you get some bad waste vegetable oil. I'm not sure I understand what you mean by changing the oil.

We are discussing waste vegetable oil as an alternative fuel. Removing food particles and water is an issue. Some folks don't get super clean oil and need to be able to remove contaminants.

 

Sorry - since all I saw was one post, I thought you meant motor oil.

For cleaning veg oil, when I used to live in an area where one could run it (or Biodiesel) we just used large plastic 55-gal drums and let the contaminants settle. Filtering with a metal screen prior to dumping it in the barrel. And then not using the bottom 1/5 of the barrel - ever...