Winter DEF Maintenance Tips

Medium Duty New Vocational Kenworth Truck

The pandemic has pushed trucks and other fleet vehicles out of service for long periods of time due to event cancellations and reduced road travel. As more vehicles get put back into service, one of the easiest details to overlook is the diesel exhaust fluid (DEF) that is already in the vehicle. DEF has a limited life and may need to be changed before a vehicle goes back into service.

According to the American Petroleum Institute (API), a truck’s DEF storage life is about 12 months in optimal conditions. If it’s been in the vehicle for longer, it should be drained and replaced.

Winter Maintenance
DEF freezes at 11 degrees and requires proper maintenance or dispensary to preserve quality. DEF expands up to 7 percent when it becomes frozen. It can damage the storage tank if it’s full as it freezes.

If DEF freezes in your truck, you don’t need to insert additives in the tank to melt it. DEF needs to remain pure for it to work properly. Your DEF tank has a heating element that quickly thaws the DEF, so your truck will start without any issues. On-spec DEF is specifically formulated to allow fluids to thaw at the proper concentration to keep your vehicle operating smoothly.

Other winter considerations:

  • Monitor expiration dates and use products before they expire. If you can’t find a date, ask your local distributor for the most recently delivered DEF products.
  • Check bottle labels for recommended storage temperatures.
  • Look for API certification marks on the bottle.

Does your DEF require maintenance? Visit to view our DEF products today!

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