I thought to provide an update on my first few days of experience after having the 48-gallon Titan replacement tank installed.
I did lay a huge piece of cardboard on the driveway under the new tank for a couple days, just to ensure no leaks, and not a drop on the cardboard so I pulled that out after having confidence I wouldn't be leaking any diesel on the driveway.
I did crawl under the truck before and after the replacement tank install to see what loss of ground clearance happened because of the bigger tank. My King Ranch has FX4 package, so the measured distance from the bottom of the skid plate under the fuel tank to the ground was 10.75" from factory. After the Titan replacement tank install, I lost ~0.75" of ground clearance as I measured just a touch under 10"; however, looking over the rest of the bottom of the truck with the other skid plates and rear differential I would say that my overall ground clearance was not impacted by the Titan tank. This was a relief to me as I do some off-road fishing up in NW Ontario.
Next, just as I expected, the sliver of orange when 50 miles to empty is just that--a sliver! The 4th attached photo is 47 mi to E with the OEM tank, which is reading about 1/8th tank. The 1st attached photo below is 50 mi to E with the Titan tank, and as you can see it is pretty much on the E line.
Now to the first fuel up. Total fill up elapsed time 7 minutes 2 seconds, and would have been ~5 mins if I didn't have to hang up the pump and start over because I hit the $125 credit card sale limitation--I will fuel up sooner in the future to avoid that. The truck initially reported 815 mi to E as can be seen in the 2nd attached photo below. I knew that wasn't correct, and figured that the truck's computer would have to re-learn distance to empty calculations with the larger tank size. I thought about maybe disconnecting and reconnecting the positive battery terminal thinking that may re-learn it faster, but decided to just see what happens. As can see in the 3rd attached photo below, I did 276.9 miles of fiberglass boat towing since the full tank, and it is now telling me 617 mi to E at just under 3/4 tank, and that is all towing miles at ~17.2 mpg.
It is yet to be seen, but 276.9 + 617 = 893.9 towing miles on this 48-gallon tank. 893.9/48 = 18.62 mpg, whereas truck is reporting 17.2 mpg. And, we all know 0 mi to E is not truly empty and there is still 1-1.5 gallons in most vehicles when reaching 0 to E. Let's go with 1.5, that would mean 893.9/46.5 = 19.22 mpg. Moral to the story is that I need to drive this fuel tank down to 1/4-1/8th tank and fuel up to full and hand calculate mpg's to see where I am at compared to what the truck computer is telling me. Before the new tank, I was within 1 mpg between the two (there is an easy way to recalibrate this if I need to, but going to track for several tanks before I would make any recalibration adjustments). Since we are into open water fishing season now, I will be putting on a lot of towing miles coming up.
I will provide another update in about a week or so after having some more data points to share.