Don't use bio if you have a DPF. The older (7.3L PS's) are fine with it, actually probably better because bio has more lubricating properties than ULSD. With a 6.0L I would be a little dubious about it, most of the newer diesels were build to run on ULSD. Up to a 25% mix I doubt would hurt much, but more than that is asking for trouble IMO.
We run 15% bio in our hostler trucks at work since its cheaper (they all use 5.9L Cummins 4 spd Allison trannies, 152 hp mechanical 10.36 gears and 200 hp 7.16 gears electronic). The new one has a DPF and its CONSTANTLY cycling because it plugs up so quickly, the newer non-DPF electronic ones have all sorts of EGR issues from buildup, and the older mechanical engines LOVE the stuff. Thats what I've found with bio, older diesels like it and the newer ones don't. The older Toyota and VW diesels really like the stuff too. LR
'09 Ford Ranger FX4 with a mean owner