A few things to consider. You will almost never find certified ASTM spec biodiesel in home brew or co-op situations. The tests are very rigorous and expensive. Having said that, an IDI does not need ASTM spec fuel to run very well, nor do most older diesel engines. Any mistakes that you or whoever made the fuel made in the brewing process will take you to the proverbial woodshed and continue to do so sometimes long after you've burnt the offending batch of fuel. This usually manifests itself with plugging of fuel filters. There is no doubt with biodiesel that you will be changing filters more frequently than with good quality pump stuff. However, I find the tradeoff worthwhile, the engine runs a little cleaner and I save lots of money, in fact I'm probably paying similar prices for my homebrew to what we were paying at the pump in the 80s when these trucks were designed, the only reason I can afford to drive a vehicle that gets 12-16 mpg. If I had to pay pump prices I'd be walking most likely. Gus and Smolkin are right about the rubber fuel system components. Any cheap N-Butyl rubber or natural rubber has to go. Viton and Neoprene are the preferred materials. As mentioned the expensive fuel injection rated hose is also very good. I have yet to find fuel return lines and injector orings that cn tolerate B100 but Typ4 was good enough to send me a few of his Viton orings. I will report back on how they hold up, I'm also going to use some alcohol grade, AN or Tygon fuel hose(as Gus uses for his WMO setup) for the return lines and see how they hold up. Personally I think you probably did the right thing to pass on the bad fuel from the 6.4. I'm not sure I'd run high blends of bio in a 6.4, so it might have been that the 6.4 is too tempermental for B100. On the other hand I see your location is in PA and I know you guys have had a heck of a winter up there. As mentioned even ASTM spec B100 gels a lot higher than D2 depending on what the feedstock oil was. My guess is he got caught with a tank full of high biodiesel blend and you guys had some cold weather come through and he wound up with a chunk of lard in his tank. This time of year I'd say in your climate you probably can only run very low blends or else you need heated tanks.