I'm butting in here even though mine is a 3rd gen, '06 model. I travel around the country quite a bit and have found that non-bio diesel is getting more difficult to find. As a result, I've used B-20 a number of times even though I didn't want too. The result has been clogged fuel filter from the higher dissolving properties of the Bio, loosening up tars and shellac adhering to the tank and lines (I assume) and a need to change it more frequently. I don't know and can't get definite answers as to what damage might be occurring, long term. Does anyone know? I have over 141K miles, mostly towing.
Unlike big rigs all OEM's for pickups and passenger vehicle diesels have been skimping of water separators and fuel filters forever. Cummins in the past offered Government fleets the ability to go up to 20% Bio and the only difference is additional water separators added to the B20 units.
Biodiesel adsorbs more water than #2 ULSD and today's ULSD will hold more water in the fuel than LSD and older obsolete spec diesel fuel of the past. Simply put to run Biodiesel "contaminated" fuel that lawmakers think is a good idea to force on us you need a good water separator and good fuel filter. The upside is Biodiesel is one way to provide fuel lube that the ULSD process ruined. Avoid yellow metals like brass fittings as bio corrodes these. Worst case is you get hit with the diesel bug and the bugs go nuts with Bio Diesel. Even then better than the beancounter garbage OEM wanabe water separator filters can save your injection system. (Save here means you don't replace it now, but, may have to run a special cleaner from a 5 gal pail through the system.) This said I have thousands of miles running B99 just fine until their 'wet fuel' quit meeting spec and the bugs hit hard.
https://www.turbodieselregister.com/threads/248698-ULSD-and-Biodiesel-Exposed!
Oh yeah, you also need to change your oil more often as BioDiesel doesn't evaporate back out of the oil like #2 diesel does and UOA doesn't detect it as "fuel": Viscosity of the oil falling off is a clue. Post injection to clean DPF designs get hit the worst as a good amount of the bio hits the cylinder walls rather than evaporating.
Again:
1) Run a separate water separator and better fuel filter than OEM (may exclude the late models that finally address this long standing skimp area.)
2) Run a dose of biocide now and then.
3) MPG and power loss is around 10% depending on Bio percent. 10% MPG and power loss is biased off running B99 on a daily parts delivery route towing.
4) Change oil more often.
5) Storage is a concern, just ask boaters who store their boats long times...
6) Nox emissions will be higher while soot goes down.

ok to make our fuel emit more NOx but not for VW...