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et2's avatar
et2
Explorer
Aug 05, 2013

DEF fluid long term storage

Understanding DEF fluid doesn't store too well, what to you people with motor homes do in cold climates where your rigs sit for 6 mths or longer? Drain it? Ever have problems with 6 month old Fluid?

Thanks

6 Replies

  • Sprinters have two DEF tank sizes available. One of them is smaller (around 4000 miles) and is generally specced for type "B" rigs so there is more room under the hood for batteries (and alternator charging.) The other is the 9000 mile size.

    One caveat. If filling the DEF tank, fill it completely. Otherwise the Sprinter's computer will remain saying it is low.
  • I just don't fill it up all the way. My tank is so huge it lasted 9000 miles from new. A lot of newer Sprinters are coming with smaller tanks which helps.
  • Freezing will not hurt it, though it could break the container it comes in.
  • DEF stores for two years from its date of production. Lots of erroneous error codes generated on vehicles stating bad quality DEF when the problem has actually been one of the NOx sensors. It is mostly water so it should be stored where it will not freeze.
  • Heat and light are the enemy. My pickup has gone for a few months without filling and its never been a problem and in 2 1/2 years has never been drained and flushed, same goes for our Mercedes.
  • In theory, one takes the vehicle in for servicing every 10 months or so, and part of the process is draining/flushing the DEF tank so any urea crystals are removed.

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