At about 6,500 mi. on the ODO, the idiot light came on for more DEF. This seemed awfully early. However I realized we don't know how much was in it out of the factory (though should be full, theoretically), and we never added any before. I added the one gallon I carry plus a 2.5 gal. jug I was able to buy at the service station. It showed no signs of being full so it likely needs more.
Filling the DEF was a bloody mess. Even with the 1-gal. container, hitting the tiny inlet was very hard. It was impossible while trying to juggle the 2.5 gal. jug. (No, it did not have any filling tub with it!) I pirated a funnel from the kitchen and it's now officially mine. Even so I had to transfer at least half of the 2.5 gal. jug into the 1 gal. jug before attempting to load using the funnel. It's the most ridiculous loading system ever.
Here's a good video (on the linked page) about dispensing DEF from a pump and using the magnetic mis-filling prevention device:
See also this helpful PDF:
Land of 10,000 Lakes
2016 Forester MBS 2401R
Nights camped 2016: 29; RV to date: 32