Back to the warranty issue, here is a presentation from a gov lab that seems to agree with the plaintiffs and addresses the 5% rule of OEMs.
http://www.eere.energy.gov/cleanciti...ck_webcast.pdf

Biodiesel Warranty Issues
•Manufacturers warrant their products against defects in
materials and workmanship
•In general use of a particular fuel should have no effect on the
materials and workmanship warranty
•Use of biodiesel does not “void the warranty”, this is prohibited
by the Magnuson-Moss Warranty Act
•Manufacturers are concerned that extensive use of biodiesel will
result in increased numbers of warranty claims for what are
actually problems caused by the fuel
Engine and vehicle manufacturers are generally comfortable
with blends up to 5%
Concerns about fuel quality and stability are what is preventing
approval of blending levels above 5% for most manufacturers

Warranty Statements
While manufacturers do not warrant fuel, many have position statements
and recommendations on biodiesel:

Ford Up to 5% biodiesel, must meet both ASTM D6751 and EN 14214.

International Approve up to 20% biodiesel, must meet ASTM D6751.