The fuel is not an issue. They (EPA) just changed the requirements to a 'low sulphur', which is the 15ppm you keep seeing. They all run on the stuff. Is it as good for the engine as the high sulfur? I suspect not. Kind of like when they took lead out of our regular gasoline. Switch worried folks.
And you'll get a earful on the 6.0's, the 7.3's, the Cummin's, the etc etc.
Take it all with a grain of salt. Some of us are blind to what we want to believe because we bought a certain rig and we want to know that we made the 'best' decision. Some have had a bad experience and therefore everyone else will too. There are some common problems with different years of every engine out there. Read, but read between the lines too.
Have owned all three makes.. some real trucks also. They ALL have issues. The fact that you are a low mileage user is hugely in your favor.
Bottome line; fuel is not an issue.
Edit: Buzzcut beat my post... and is right about the additive. Most don't add it, but it is how one makes up for the change. He's also correct on the difference between power on the 6.7 to the 6.0. Huge. But, the 6.0 gets down the road just fine. Life ain't a race.