If you have been told your warranty is no longer valid because you used biodiesel, or that it will be voided if you use biodiesel at any point in the future, you have been given inaccurate information.
A manufacturer cannot legally void the warranty on a vehicle due to the fuel used in the engine unless they can prove that the fuel caused or contributed to the failure in the vehicle (per the Magnuson Moss Warranty Act. (15 U.S.C. 2302(C)). If Fusion is ever proven to be the direct cause of failure to any OEM-warranted fuel system materials, Blue Sun will repair or replace the damaged material at no cost.
If your vehicle manufacturer fails to honor emission/warranty claims, contact the EPA at (202) 260-2080 or www.epa.gov. If federal warranty protection is denied, contact the FTC at (202) 326-3128 or www.ftc.gov.
Excerpt from Magnuson Moss Warranty Act. (15 U.S.C. 2302(C))
Section 2302. Rules governing contents of warranties
(c) Prohibition on conditions for written or implied warranty; waiver by Commission No warrantor of a consumer product may condition his written or implied warranty of such product on the consumer's using, in connection with such product, any article or service (other than article or service provided without charge under the terms of the warranty) which is identified by brand, trade, or corporate name; except that the prohibition of this subsection may be waived by the Commission if -
(1) the warrantor satisfies the Commission that the warranted product will function properly only if the article or service so identified is used in connection with the warranted product, and
(2) the Commission finds that such a waiver is in the public interest. The Commission shall identify in the Federal Register, and permit public comment on, all applications for waiver of the prohibition of this subsection, and shall publish in the Federal Register its disposition of any such application, including the reasons therefor.