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hink about changing diesel exhaust fluid (DEF) in vehicles that have been idle for a prolonged period. You should also protect DEF from extreme cold to keep Diesel-powered vehicles running smoothly.
With recent months being dominated by challenges caused by COVID-19, some dieselpowered vehicles have likely been out of service for a long period of time. This includes buses, motorcoaches, trucks and other fleet vehicles that have been idle for many months due to school closures, the cancelation of events and reduced road travel.
DEF Maintenance on Idle Vehicles by Jeffrey Harmening, American Petroleum Institute
As operators of various fleets manage the maintenance needs of vehicles that are out of service or those to be put back into service, there are many items that need to be considered. One of the easiest items to overlook is diesel exhaust fluid that is already in the vehicle. DEF has a limited life and may need to be changed before a vehicle goes back into service. The American Petroleum Institute (API) recommends that you determine when DEF was put in the vehicle. The storage life of DEF is about 12 months in optimal conditions. In the case when DEF has been stored in the vehicle past 12 months, it is recommended that it be drained and replaced. API also recommends changing the DEF if a vehicle sat unused in summer heat for a prolonged period of time or if the DEF may have been contaminated in any way. In addition, API suggests changing the engine oil if you believe moisture may have built up in the engine; plus check other critical fluids and vehicle components including the tires before going back out on the road. Also, remember to evaluate the DEF on shelves in the shop if it has been a long time since the last delivery. Order new DEF if necessary as you do not want to replace old DEF in your vehicle with product that is expired. DEF is not considered a hazardous material but should be disposed of in accordance with local regulations.
Managing DEF in Wintertime Made from a mixture of technically pure urea and purified water, DEF freezes at 11 degrees Fahrenheit and -11 degrees Celsius and needs to be properly maintained and dispensed to preserve its quality. Like water, DEF will expand up to seven percent when frozen and can damage the 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.
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. The vehicle will start without a problem and the DEF tank has a heating element that can quickly thaw the DEF. Do not worry; on-spec DEF is specifically formulated to allow the 28 • National Bus Trader / December, 2021
With many buses sitting idle, it is important to know that diesel exhaust fluid (DEF) has a limited storage life. Under optimal conditions, the storage life of DEF is about 12 months. It should be drained and replaced if it goes beyond this time, if it sat unused in the summer heat for a prolonged period, or if it has been contaminated in any way. AMERICAN PETROLEUM INSTITUTE.
