DEF

I've used the truck stop DEF pumps once or twice, but even though my DEF fill is on the driver's side, it's so far back that I have to pull up partway after filling the diesel tank. So I mostly use the Blue DEF "boxes" from Wal-Mart, and generally add one (2-1/2 gallons) for each fill-up (usually around 90-100 gallons in my 150-gallon tank). That ratio seems to work out about right. I track my fuel use carefully, but haven't bothered to monitor my DEF usage any closer than this.