Protect Your Diesel Car or Truck from Extreme Cold this Winter Don’t Overlook DEF to Keep Your Vehicle Running Smoothly


Harmening, Manager – EOLCS/DEF/MOM, American Petroleum Institute Diesel Exhaust FluidDiesel Exhaust FluidAccording to the Farmer’s Almanac, the winter of 2019-2020 will be filled with bitterly cold weather in the eastern parts of the Rockies and east to the Appalachians. The Northeast should also experience very cold temperatures as well. For those living in areas that experience significant cold, there are always a few things that you need to prepare for as winter sets in. 

One thing that may be overlooked is the proper care of Diesel Exhaust Fluid (DEF) used in many cars and trucks with diesel engines. Handling and storing DEF can be challenging in wintertime for drivers filling up on the road and for those storing it in a garage or shop. Made from a mixture of technically pure urea and purified water, DEF freezes at 11 degrees Fahrenheit and needs to be properly maintained and dispensed to preserve its quality. Some things to keep in mind about DEF use and storage include the following: 

  • If DEF freezes in the vehicle, do not put any additives in the tank to help it melt. DEF needs to remain pure for it to work correctly. 
  • In cold weather, the vehicle will start without a problem and the DEF tank on the vehicle has a heating element that can quickly thaw the DEF. Don’t worry; on-spec DEF is specifically formulated to allow the fluid to thaw at the proper concentration to keep your vehicle operating smoothly. 
  • Like water, DEF will expand up to seven percent when frozen and can damage a storage tank if it is full or nearly full when it freezes. Keeping a tank that you think may freeze less than full is a good idea. 

In addition to cold, there are other things to consider when purchasing, storing and handling DEF. 

  • When purchasing DEF in containers be sure to look at the expiration date on the bottle and use it before this date as the product has a limited shelf life. 
  • Look for the API certification mark on the bottle as well. Many diesel engine manufacturers recommend that drivers use API-licensed DEF. 
  • DEF can be expected to have a minimum shelf life of 12 months or even longer in optimum conditions. Check the label for recommended storage temperatures. API recommends that you don’t store if for too long in your car or truck once you purchase it. 
  • Use dedicated equipment for dispensing DEF. Don’t use funnels, pitchers, hoses, etc. that you may use for other fluids when putting DEF in a tank. 
  • Anything used for dispensing DEF should be cleaned with distilled or de-ionized water and followed by a DEF rinse. Don’t use tap water for cleaning. 

The quality of the DEF going into your vehicle is as important as the quality of the engine oils or fuels used in your vehicles. Use of API-licensed Diesel Exhaust Fluid will ensure that the DEF meets the high standards required by engine and vehicle manufacturers.