In my area there is one Exxon station that normally has the best price for diesel, anywhere from $0.10-0.15/gal less that most of the other places. I do not the "Diesel is not an Exxon branded fuel" label on the pump (same at other Exxon stations), but have not had any problems with the fuel.

I do my 5k oil changes, 10k fuel filter changes, always use fuel additive (generally Motorcraft) and I do UOA on every oil change. I've also done a number of cross country trips where I'm sure I've had some bio-blend, but it has not shown up as any different in the UOAs.

The only thing that shows up in the UOAs is if I've had a period with a few interrupted DPF regens, as long as I let regens complete fuel dilution stays around 0.5% or less.