Many years ago Mother Earth New published a design to filter waste oil to use in a waste oil heater. It was basically a long filter column of a stack of toilet paper rolls maybe 10 or more a solid core support center with a tube or duct large enough to fit the rolls in. waste oil was poured into top of column drained into pan at bottom an incandescent light bulb was place over the top of the oil surface which served to evaporate the volatile organic compounds. The result was said to give a consistent 30 W
oil suitable to reuse in an engine for those who recycle their oil. A friend of mine in Canada a garage mechanic built one to improve the consistency of his waste oil burner. Since he had a virtually unlimited supply of waste oil, he not only heated his shop but build a larger forced air unit that he heated his entire house with during those Canadian winters for free. He also build an electric car out of a 1960's dodge dart removed the engine beefed up the suspension and filled the engine compartment the trunk and the back seat with old car batteries. With a 5hp generator that sat in the trunk to provide a surface charge when he was stopped in traffic. He put the car on charge at home and at the shop. Claimed he got better than 150 mpg and could drive for about 100 miles between charges. The motor was a 20hp DC surplus starter motor. He utilized the existing transmission on the car top speed was only about 45mph. This was back in the 1970's and I very much admired him.