DEF- The Importance of Proper Handling

Diesel Exhaust Fluid (DEF) – An aqueous fluid made of 32.5% urea and 67.5% deionized water.

Due to the increase changes of emission restrictions and guidelines. DEF is showing up more & more in equipment. However DEF needs to be carefully handled to prevent contamination of the DEF system and engine failure. Listed are some key points about DEF”

  • DEF is non-hazardous, if spilled, simply flush with water.
  • Tier IV final engines above 75 HP require DEF.
  • DEF fluid freezes at 12 degrees Fahrenheit.
  • DEF fluid has a shelf life of 12-18-24 months depending on environment.
  • Only use dedicated storing and dispensing containers. Do not use funnels or bottles that have been used for other liquids.
  • Cannot be store in direct sunlight.
  • DEF cannot be topped off with water.
  • DEF systems utilize a DEF quality sensor that detects contamination.
  • If DEF becomes contaminated, engine will derate and damage to the SCR (exhaust system) will occur, and lead to potential engine failure.
  • Do not reuse DEF containers.
  • DEF can only come in contact with titanium, rubber, plastic and stainless steel.
  • DO NOT start a diesel engine if DEF has been added to the diesel tank.

  • Below is a short video by Thoroughbred Diesel on the proper filling procedure of DEF: