We used to buy DEF in bulk. It was ok if you pumped directly into the truck, or machine, but if you filled jugs, it seemed to crystalize in the jug. If you only used part of a jug, you get the crystals, in the left over jug. Since we started buying jugs for the machinery, there is still a bulk tank for the trucks, no issues in the warmer weather. A lot of times, if the lines don't drain back into the tank, they will freeze over night. I know lots of guys that just shut down, and kill the master switch before the purge is finished. We have had a lot of issues with the gauge showing a full tank, when it's not full, and in winter, there are multiple drivers, so not always sure if they are full or not. Any trucks that are no longer under warranty, strangely enough their DEF tanks are full of washer fluid, and are trouble free.