Most Diesels can't run on vegtable oil because it's too thick, dosen't atomise properly and if you have a direct injection engine it gums up the piston rings like a fryingpan.
Any diesel can be run on well made bio, thats fact regardless of what anyone else says.
The problem comes with how well it's made. During the proccess of making Biodiesel you use Methanol. Problem is methanol eats seals for breakfast, lunch, dinner and it will go back for supper. You use Sodium Hidroxide to remove the methanol from the fuel.

Someone in a shed making the biodiesel for them selves will perfect the art of making sure all methanol is removed from the biodiesel before it goes anywhere near the car.
Someone who sells it in massive batches out of a warehouse won't which is where the scaremongering stories come from.
There ought to be a set of standards for selling biodiesel that have to be adheard to.