I have been looking into running biodiesel in a 6.7 powerstroke for my own use not so much saving money mainly saving the environment if that’s a thing still. The real issue with the bio in our emission equipped trucks is Regen process. The diesel alone can delute our oil systems and the bio fuel is even worse at much worse your truck will “run fine” on B100 but when it goes into Regen you get get an extra gallon of bio fuel in your crankcase which will eventually harm the motor. This is why 6.7 are rated for b20 as this isn’t high enough to cause major problems the b5 rating on 6.4 is really just because they had to give it a rating it’s when biodiesel first became big. b30 May also not be too much most manufactures recommend tighter standards than truly needed but I am going to run my 6.7 once deleted on B100 once I have more than a few thousands miles on it. I just want to drive 40-50k miles some long hard loads on it to make sure I don’t have a lemon from the factory before I void my warranty. I am no expert but from the engineer I knew that worked at GM this is why the pit the 9th injector design on there engines

The b5 vs b20 difference in 6.4 vs 6.7 is simply due to emissions compliance. The 6.7 can do b20 becuase of the Def fluid .