DEF has a shelf life. Boxed DEF has a month/date label. Shelf life is dependent upon temperature stored.... the higher the temperature the shorter the life. You should be able to search internet and find out shelf life vs. temperature. Considered it a problem in early on travels, but have not worried too much about it lately. Always run DEF tank to near empty before refilling on first outing. My trips are annual with long trips when we go out. Have used bulk DEF with no problems, but you just don't know it's age.
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