I finally decided to change the ptu fluid on my girlfriend's 2018 Journey after reading the whole thread. I'm not the most car-savvy person, so I wanted to make sure I knew the entire process before starting. This tip about the tubing is probably the best piece of advice on this thread. I used one foot of the 1/2" ID and two feet of the 1/4" OD. I would not recommend using anything shorter than this. I got the smaller hose all the way up until the start of the black hose.
The warm oil went down pretty slow, so I realized that, at the risk of potentially tasting what ptu fluid tastes like, alternating between positive and negative pressure on the "straw" helps the oil go down even faster. BUT, if you are able, shove the small tube into the black vent hose. Then, slowly apply negative pressure (making sure to let go before you swallow oil) and watch the oil from the large tube drain much more quickly. This pulls (mostly air but a little oil) up the straw, which is enough to make the oil fall down into the vent hose.
Also, I wasn't able to get to the ptu vent without removing the filter housing. It's four 8mm bolts, so it's not too complicated.
As for service intervals, her car is at 64k miles (103k km), and the ptu fluid was brown. It definitely wasn't clear, but it looked much, much better than the rear diff which was pitch black at 62k (I flushed it again at 63k to get even more crud out). I imagine I will start changing the rear diff fluid every 20-30k miles, but the PTU fluid should be ok for another 60k.
