Around here we deep fry in our very own extra virgin olive oil, and we use the same simple technique our grandmother used to keep the oil clean, a neat trick that works like a charm: to keep the oil clean while you deep fry, add a couple 2 inch chunks of raw peeled carrot to the pan right when you add in whatever food you are frying.
The carrot pieces act like a magnet, attracting any crumbs or blackened bits to themselves and keeping the oil itself nice and clean.
Whether you are frying schnitzels, potato pancakes, or anything else, this works great.