I thought you guys might be interested in Ford's answer to my question to them about running biodiesel in my truck. I wanted an official answer. I hope you find it useful. Here is their response:

Thank you for contacting the Ford Motor Company Customer Relationship Center regarding the use of biodiesel fuel.

Fuels containing no more than 5% biodiesel may be used in Ford diesel powered vehicles.
There are still some unresolved technical concerns with the use of biodiesel at concentration greater than 5%. Some of the concerns are as follows:

- Special care is required at low temperatures to avoid an excessive rise in viscosity and loss of fluidity
- Storage is a problem due to higher then normal risk of microbial contamination due to water absorption, as well as a higher rate of oxidation stability which creates insoluble gums and sediment deposits
- As it is hygroscopic, the fuel tends to have increased water content, which increases the risk of corrosion
- Biodiesel tends to cause higher engine deposit formations
- The methyl esters in biodiesel fuel may attack the seals and composite materials used in vehicle fuel systems
- It may attack certain metals such as zinc, copper based alloys, cast iron, tin, lead, cobalt, and manganese
- It is an effective solvent, and can act as a paint stripper
- It tends to loosen deposits in the bottom of fuel tanks of vehicles previously run on mineral diesel.

Should you require additional information about this matter, please contact the service department at your local Ford dealership. To locate a Ford or Lincoln-Mercury dealership, please visit www.genuineflmservice.com.

We consider the satisfaction of our customers one of our most important objectives. If you have any other inquiries or concerns, please feel free to contact us and we will be happy to address them for you.

Sincerely,
Maisha
Customer Relationship Center
Ford Motor Company