Diesel Exhaust Fluid (DEF) is a mixture of 32.5% urea and 67.5% deionized water. DEF freezes at 12o F (-11o C), but low temperatures will not cause the DEF solution to degrade. Regardless, it is recommended that DEF be stored at temperatures above its freezing point so it’s always ready for use. Methods for heating and maintaining temperature in large totes, tanks, and containers can best be achieved with a Powerblanket DEF Heater.
High temperatures is where we run into problems with DEF degradation. High Temperature will cause DEF to break down and can limit its shelf life. DEF begins to decompose into isocyanic acid (ammonia) at temperatures above 122o F (50o C). Diesel-powered vehicles that utilize urea SCR systems require fresh, uncompromised DEF in order to work correctly. In order to limit DEF decomposition during storage, it is recommended that it be kept between 23o F and 86o F (-5o C and 30o C) and that it be placed away from direct sunlight.
Shelf Life is a function of Ambient Storage Temperature. Listed below is a chart outlining the guide for shelf life based on ISO 22241-3 specifications.
|..Temperature º F
||..Temperature º C
||Minimum Shelf Life
|< 50º F
||< 10º C
|< 77º F
||< 25º C
|< 86º F
||< 30º C
|< 95º F
||< 35º C
Q & A
Q. How do I keep the DEF from freezing and what happens if the DEF freezes in the tank on my vehicle?
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. Does DEF expand when frozen?
A. Yes, DEF expands by approximately 7% when frozen. DEF packaging and tanks are designed to allow for expansion.
Q. How much DEF will a truck consume?
A. DEF consumption is expected to be approximately 2% of fuel consumption, depending on vehicle operation, duty cycle, geography, load ratings, etc.
Q. What is the number of miles a truck can expect to travel on one gallon of DEF?
A. DEF consumption is directly related to fuel consumption. A truck averaging 6 MPG can expect to go approximately 300 miles on one gallon of DEF.
Q. How can an operator determine how much DEF they will need/use?
A. DEF consumption will be approximately 2% of the diesel fuel consumed. Another way to consider it is that DEF will be consumed on a 50 to 1 ratio with diesel. (For every 50 gallons of diesel fuel burned, you will use 1 gallon of DEF). If you know the average fuel consumption of a vehicle, you can easily calculate the amount of DEF that will be used.
Q. Is the DEF dose rate the same for all engine manufacturers?
A. The DEF dose rate will vary slightly amongst engine manufacturers. While most engines will have a dose rate of 2 percent of diesel fuel consumed, the dose rate will range from 1 percent to 3 percent.
Q. What happens if the vehicle runs out of DEF?
A. Vehicles that use DEF will have indicators on the dash that will alert the driver of the quantity of DEF on board. A gauge similar to a fuel gauge will indicate the level of DEF. There will be a DEF low level warning lamp that will illuminate when DEF is low. If the vehicle is operated such that one would run completely out of DEF, vehicle power will be reduced enough to encourage the operator to refill the DEF tank. Once the tank has been refilled the engine will resume normal power levels
Q. What is the recommend solution for temperature control of DEF at refilling stations and storage facilities?