this is also why I don't typically 'store' jugs of DEF, as they are relatively easy to find, and any Walmart has the 2 1/2 jugs I prefer anyway.
If you look at a used DEF container's flexible hose, after it has sat for a while, it is dried out white 'cakey' stuff...which I imagine could also happen in a tank if it sits for too long...months, I mean.
and, yes, periodically you can hear your engine 'revving up' as the regen process takes place, whether while driving, or while idling...
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