Let's talk about DEF

Every day our Parts Professionals answer questions about Diesel Exhaust Fluid, and of course you already know that we carry DEF and the full line of DEF handling equipment, from hand pumps for barrels to powerful electric pumps for bulk storage totes and replacement parts. All of this and our DEF is the best price in town. Whether it’s a 10 litre jug, a 205 litre drum or a 1040 litre tote, we stock it for you at all times.

We’ve put together a Q&A with the most frequently asked questions about DEF for you. Let’s dig in, shall we?



Q: What is Diesel Exhaust Fluid (DEF)?

A: It is a non-hazardous solution, which is 32.5% urea and 67.5% de-ionized water. DEF is sprayed into the exhaust stream of diesel vehicles to break down dangerous NOx emissions into harmless nitrogen and water. This system is called Selective Catalytic Reduction (SCR). 

Q: How much DEF do I need?

A: The amount of DEF consumed by your equipment varies depending on the size and make of the engine you’re running, how the engine is configured, and the load you put on it. Load factors and idle time play a big role here. Off road machines that use a full SCR system may consume DEF at a rate of 8 to 10 percent of fuel burned, to help control the NOX.

Q: How will I know that the DEF product I purchase will work?

A: The DEF you purchase should state and display the certification of the International Organization for Standardization ISO 22241. This will ensure the proper purity and concentration (32.5%) of urea.

Q: What is the freeze point of DEF?

A 32.5% solution of DEF will begin to crystallize and freeze at 12F (-11C). At 32.5%, both the urea and water will freeze at the same rate, ensuring that as it thaws, the fluid does not become diluted, or over concentrated. The freezing and unthawing of DEF will not cause degradation of the product.DEF expands by approximately 7% when frozen. DEF packaging and tanks are designed to allow for expansion

Q: What happens if the DEF freezes in the tank on my equipment?

A: During vehicle operation, SCR systems are designed to provide heating for the DEF tank and supply lines. If DEF freezes when the vehicle is shut down, start up and normal operation of the vehicle will not be inhibited. The SCR heating system is designed to quickly return the DEF to liquid form and the operation of the vehicle will not be impacted. The freezing and unthawing of DEF will not cause degradation of the product.

Q: Are there special storage requirements for DEF?

A: DEF should be stored in a cool, dry, well-ventilated area, out of direct sunlight. While the optimum storage temperature is up to 77F, temporary exposure to higher temperatures has little to no impact on the quality of DEF.

Q: What is the shelf life of DEF?

A: If DEF is stored at ambient temperatures of 77F with no major periods of exposure to heat over 86 F then the batch of DEF will last roughly two years. If a package of DEF is exposed to periods of heating the fluid will last approximately one year.

Q: Should I be concerned about handling DEF?

A: No. DEF is a nontoxic, nonpolluting, non-hazardous and nonflammable solution. It is stable, colorless, and meets accepted international standards for purity and composition. DEF is safe to handle and store and poses no serious risk to humans, animals, equipment or the environment when handled properly.

Q: Is DEF corrosive?

A: DEF is corrosive to copper and brass as well as other materials. Only approved materials, such as high density polyethylene (HDPE) are used in the DEF tank, packaging and dispensing equipment.

Q: Is any maintenance required on the DEF Dosing Unit Filter?

A: The DEF Dosing Unit Filter will need to be replaced as part of routine maintenance.