The lowest price on DEF that I otherwise know of is BlueDEF by Peak at Sam's, which is about $10.xx for 2.5g.
There are a couple of new Buc-Eee's truck stops nearby that are HUGE, and they have SuperS DEF for something around $2.5g. Since it's ISO 22241 approved, I'm trying to think why I wouldn't want to use it? I would imagine that it has to be as fresh as can be with all the big trucks using it.
Does the pump handle shut off when the tank is full, like it does with gas/diesel? Definitely don't want that stuff spitting back up at me. Guess I could just watch meter on the pump, since I know what my gauge reads and how big the DEF tank is.
SUPER S DIESEL EXHAUST FLUID: Smitty's Supply, Inc.