I can't blame the engine manufactures for the delay as the problem is guaranteeing the quality of fuel. Even here in Atlanta, I knew of someone that was purchasing Bio diesel from a reputable fuel dealer only to find out that somehow (and yes, it could have been accidental, just to give the benefit of the doubt) that the Bio diesel was contaminated with straight WVO (luckily, it was filtered and dewatered). Regardless, until production is greater, the manufacturers will be cautious. That is why they are doing it in increments, such as B5 for some and up to B20 for others.
It's almost a bit ironic as back in the 70s, the European car manufactures were hesitant because of the quality of #2 in the states. It was a lot less quality controlled than in Europe at that time....

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87 300SDL - 215K Miles !!
99 F-350CC Dually PSD - 190K
86 300SDL - 189K
All on B-100