How to Convert Used Motor Oil to Diesel

Updated March 21, 2017

"Black diesel" refers to used motor oil that has been filtered and cleansed for use by mixing it with regular diesel fuel. If you have connections with an auto mechanic or an oil-change business, you may be able to process several gallons a week for use in your diesel engine. It is important to note that impurities or sediment in the "black diesel" can potentially harm the fuel system on your diesel engine, even causing permanent and costly damage.

Put on your safety equipment, covering as much, if not all, exposed skin as possible. Also be sure that your gloves are heat resistant and can withstand temperatures up to 149 degrees Celsius. The used motor oil will be heated during the filtering process that is used to produce "black diesel."

Pour the used motor oil into a pot or flask that will only be used for producing "black diesel." Heat the motor oil on an electric burner to 149 degrees Celsius, measuring it with a cooking thermometer. Heating the motor oil will cause it to become more viscous, allowing the filtration process to be more effective.

Set up a catch pan and filter into which to pour the oil. You may want to use a plastic tarp to catch any spills or splashes that occur. Depending on the design of your filters, you may need to use a funnel to pour the oil from the pot into the filter, which will catch the impurities and allow the heated oil to pass through into the catch pan. Use progressively smaller filters, starting with the 20 micron size and going down to the smallest one that you have, which should at least be 10 microns. The more that you filter the oil, the more sediment and impurities that will be kept out of your engine's fuel system.

Use a centrifuge designed for filtering motor oil to continue straining out the oil's impurities and sediment. Some centrifuges are also capable of handling oil at heated temperatures, which can also improve the filtration process. If you are getting a lot of sediment on the filtered side of the centrifuge, continue to filter the used motor oil using the centrifuge.

Filter the used motor oil by putting it into a flask and attaching a distillery system to it. Heat the motor oil until it condenses, travels through the spiralled tubing and collects into the elevated secondary flask. Any motor oil or sediment that is left in the initial flask into which you first poured the motor oil should be recycled at an auto-parts store.

Experiment with different amounts of "black diesel" in your diesel engine. Be sure to always keep at least 50 per cent or more normal diesel fuel in your engine. Begin with a small amount of "black diesel" and continue to add more, observing the performance of your engine as you drive. If you hear ongoing and regular misfiring, then you should cut back or discontinue the use of "black diesel."

Use fuel additives and fuel injector cleaners to maintain the integrity and cleanliness of your fuel system.

Things You'll Need

  • Safety glasses
  • Protective clothing
  • Gloves
  • Pot or flask
  • Electric burner
  • Distillation system
  • 20, 15, 10-micron filter
  • Catch pan
  • Centrifuge
  • Thermometer
  • Funnel
  • Plastic tarp (optional)
  • Fuel system/injector cleaner
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About the Author

David McGuffin is a writer from Asheville, N.C. and began writing professionally in 2009. He has Bachelor of Arts degrees from the University of North Carolina, Asheville and Montreat College in history and music, and a Bachelor of Science in outdoor education. McGuffin is recognized as an Undergraduate Research Scholar for publishing original research on postmodern music theory and analysis.