Diesel Exhaust Fluid (DEF) is a non-toxic fluid composed of 32% automotive grade aqueous urea and purified water. DEF is available with a variety of storage and dispensing methods. Storage options consist of various size containers such as bulk, totes and bottles or jugs. The American Petroleum Institute rigorously tests DEF to ensure that it meets industry-wide quality standards. DEF is sometimes referred to as AdBlue in Europe and in the US.
A nationwide DEF distribution infrastructure is in place making DEF is readily available in bulk, at retail stores, online and nearly all fueling stations that carry diesel fuel. On-board tanks to store DEF typically range in size from 5 to 22 gallons and are easily identified by a blue cap and/or labeling “DEF ONLY.” For pick-up trucks and SUVs, the DEF filler port is typically located alongside the fuel filler nozzle area. (SEE IMAGE) For heavy duty tractor trailers, the DEF tank is typically alongside the diesel fuel tank on the side of the vehicle near the driver’s door. Due to the diverse nature of off-road engines and equipment, the location of the DEF tank and filler port is variable.
The DEF tank fill opening is designed to accommodate a DEF fill nozzle only to ensure only DEF is put into the tank. Diesel fuel should never be put in DEF tank and vice-versa. To protect against this misfuelling, a diesel fuel nozzle will not fit into the DEF tank opening. In addition, the DEF tank has a blue lid to differentiate it from the diesel tank which may have a yellow or green fuel cap.
For light-duty vehicles, DEF refill intervals typically occur around the time of a recommended oil change, while DEF replenishment for heavy-duty vehicles and off-road machines and equipment will vary depending on the operating conditions, hours used, miles traveled, load factors and other considerations. Typically, DEF consumption is around 3% of fuel consumption: (example:100-gal fuel consumption would consume about 3 gallons of DEF).
DEF is an integral part of the emissions control system and must be present in the tank at all times to assure continued operation of the vehicle or equipment. Low-DEF supply triggers a series of escalating visual and audible warning indicators to the driver or operator. If the DEF is not replenished, the series of operator inducements progresses and eventually can lead to derating the engine and limiting vehicle speed, and ultimately locking out the starting system.
Proper storage of DEF is required to prevent the liquid from freezing at temperatures below 12 degrees Fahrenheit. Most vehicle DEF tanks and dispensing systems have warming devices.
The U.S. Environmental Protection Agency (EPA) recently announced efforts to develop more stringent tailpipe emission standards for commercial vehicles close to zero through the “Clean Trucks Initiative.” Refinements to SCR systems including dosing strategies, catalyst packaging and location are all likely to be considered as part of future emissions compliance strategies.
