How to Recondition Old Diesel Fuel

by Samuel Sohlden
old diesel tank image by charles taylor from

Whether its on the farm or at your local gas station, diesel fuel will degrade over time. People often buy more fuel than they need and it ends up in long-term storage. Over time, the diesel fuel will become stale and require reconditioning for safe use. By reconditioning old diesel fuel, money can be saved that would have been spent on new fuel.

Step 1

Pour fifty gallons of old diesel fuel into the fifty gallon drum.

Step 2

Measure 3.125 oz. of PRD-D or 280 oz. of ether using a graduated cylinder and add it to the fifty gallons of old diesel fuel. To make measurement easier convert to liters. Every oz. converts to 29.57 ml. For fifty gallons this is 92.4 ml of PRD-D or 8.279 liters of ether. Use either PRD-D or ether to restore the fuel, but do not mix both.

Step 3

Add the fuel re-conditioner directly to the stored fuel storage if possible. The ether or PRD-D could be added directly to the old diesel fuel itself if you know its relative volume. The ratio is 5.6 oz. of ether or 0.0625 oz of PRD-D per gallon of old diesel fuel.

Step 4

Allow the old diesel to sit for a day or two. This is necessary to fully recondition the fuel.

Use the fuel as if it were fresh from the pump.


  • Avoid having to recondition old diesel fuel by adding PRD-D to it before storage. This can prevent the water contamination and biological growth that makes old diesel unusable and also serves to prevent fuel degradation.


  • Old diesel fuel can become contaminated with water. If it does, it will need to be filtered before it is used since micro-organisms such as algae and bacteria will have grown. If the fuel is only slightly contaminated with water the PRD-D will be able to neutralize it.
  • Even after reconditioning the diesel may still be unsafe to burn. Use adequate judgment before deciding to use the diesel.

Items you will need

  • PRI-D diesel fuel stabilizer and reconditioner
  • Old diesel fuel
  • Fifty gallon drum
  • Ether
  • 500 ml and liter graduated cylinders

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