How to Filter Used Motor Oil & Make Diesel Fuel

Updated April 17, 2017

Diesel engines run on a special fuel that is really a mixture of gasoline and oil. Used motor oil can be filtered and mixed with existing diesel as an additive that will double the yield of the fuel. Using old motor oil and blending it for diesel fuel has quite a few advantages in saving time and money, as well as helping the environment. Instead of searching for a way to recycle or properly dispose of used motor oil, you can reuse it in the fuel tank of the same vehicle it came out of (as long as the vehicle is diesel fuelled).

Examine the oil that you are going to use for this project. Make sure it doesn't have any liquid contaminants you can see or smell. Some contaminants common in oil from engine damage include water and antifreeze. If the oil has either of these components in it, do not use it for this project.

Connect the 15 gallon container to the paint filter system so that the output of the filter goes into the container. Connect the filter system to the large funnel acquired for this project.

Slowly pour the used motor oil out of its container into the funnel system. Be sure not to overfill the funnel, and allow time for the liquids to process through the funnel and the filter, into the 15 gallon container.

Once you have filtered all of the oil in this manner for this container, discard the used filter. Disconnect the filter system from the 15 gallon container and measure the amount of oil using the markers on the side of the container.

Add the same amount of diesel fuel into the container as you have oil. For example, if the container now has 5 gallons of filtered used motor oil, then you will add 5 gallons of diesel fuel to the container.

Place the cap tightly on the 15 gallon container and begin mixing the diesel fuel and used oil mixture. A minimum mixing time of 15 minutes is required. If the solution does not appear to be completely mixed at this time, then it should be mixed for an additional 15 minutes. Repeat until the solution is completely mixed.

Add this solution to your vehicle as you would normal diesel. It is ready to go.


Use clean containers to avoid contamination. Use clean filters each time you repeat this process. Used motor oil can come from many sources, including vehicles that no longer run.


Wear appropriate safety equipment when performing this operation (rubber gloves and goggles). Always examine the filtered oil for debris of any kind. Clean up any spills using appropriate methods, disposing of contaminated soil in accordance with EPA regulations. Check with state and local recycling companies for proper disposition of used filters and containers.

Things You'll Need

  • Used motor oil
  • Large funnel
  • 15 gallon HDPE container(s)
  • New paint filtering system
  • PVC connectors
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About the Author

Based in Texas, Michael Arcand has been a full-time writer since 2007. His articles have appeared in numerous online publications, including and Tecca. Arcand completed his CompTIA A+ certification in 2005.