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Rejuvenation of Old Fuel, Used Degreasers/Paint Thinner



Extreme care should be taken when working with ignitable wastes. 


  • Conduct activities outdoors or provide adequate ventilation by opening windows and doors and/or turning on a room fan. Stay away from potential ignition sources like pilot lights or sparks of any kind.  

  • Protective clothing such as chemical resistant gloves, eye protection and long sleeves should be worn, and care should be taken not to breathe any fumes.




  1. Carefully filter old fuels through two layers of lint-free cloth or coffee filters to remove contaminants like dirt, rust or “varnish.” 

  2. If needed, add an octane booster (available at auto supply stores or gas stations) to restore lost ignitability.  

  3. If the fuel is contaminated with small amounts of water, add a water dispersant (ethyl alcohol) or "dry gas" (isopropanol) (available at auto supply stores or gas stations) to break up the water so it doesn't enter the engine all at once.  

  4. If the fuel is contaminated with larger amounts of water, the water will sink to the bottom of the container.  Mechanically siphon the product floating above the water into an approved fuel container and rejuvenate it using the process above.  The residual water and fuel remaining in the original container will have to be stabilized for disposal.

  5. The rejuvenated fuel can then be mixed with new product at a ratio of 1 part old to 5 parts new and used as intended.  

  6. Two-stroke mixtures may be rejuvenated by filtering as above, adding about 1 quart gasoline to each gallon of two-stroke mixture, then adding enough oil to bring the mixture up to the proper ratio.  A water dispersant or “dry gas” may be added to the rejuvenated mixture if needed.




  1. Carefully filter used degreasers through two layers of lint-free cloth or coffee filters to remove contaminants.

  2. The cloth or coffee filters used to strain the degreaser should be laid out to dry outdoors in a well ventilated area away from potential ignition sources, children and pets.  The dried cloth or filters can be disposed of in the regular trash.


Paint Thinners:


  1. Pour the used thinner into a glass jar.  Tightly seal the jar and label it with the type of product and a warning not to open the jar.  Allow the paint solids to settle to the bottom of the container.  Then carefully pour the clear thinner into another container for continued use.  Make sure the new container is properly labeled.

  2. Dry the solids in the bottom of the first container by mixing them with an absorbent like clay-based kitty litter.  The dried solids can then be disposed of in the trash.


These procedures are intended for small quantities of fuel, degreaser and paint thinner from a household only.