A note of caution. I buy DEF in the jugs. A buddy did the same but fund that someone had poured out the DEF and replaced it with plain tap water, then returned the jug to the store. Now when I buy DEF in a jug I always remove the cap and check the seal to be sure someone didn't mess with it.
As for topping off.....no problem. Just do NOT run out. Those darn computer know when you do and they cannot be reasoned with!
