International has a position paper on the use of Biodiesel in their engines. They recommend max B-20. The recommendation and limitation seems to be based on uncertainty about the long term effects of using Bio. I can understand their position and I think the BioDiesel industry needs to conduct studies to overcome these reservations, which seem to be pervasive in the auto/truck makers world.
I have run a search on their tech data base and this is the most current I can find.
As I said earlier the objection seems to be of the "We just arent sure this stuff wont hurt the engine so we urge caution" type rather than "We know this stuff will damage engine components".
I really think that BD has not been an issue long enough to promote the type of research needed to validate it as an acceptable fuel, at least in the US.
I found a new Technical Service Information report from International TSI-05-12-21 dated May 2005.
It answers a big question; WHY DO FORD AND INTERNATIONAL ONLY RECOMMEND B5.
It says that Internationals position on the use of BioDiesel follows the official position of EMA (Engine Manufacturers Association).
That opinion is based on the fact that a 5% blend fuel (B5) using Bio that meets ASTM standard for BioDiesel (ASTM D 6751) also also meets the ASTM standard for Petro diesel (ASTM D 975).
Fuel that has higher concentrations of Bio do not meet the 975 standard. Work is currently underway to develop a B20 standard and the EAM will not sanction its use until this standard is developed.