It has been proposed that biodiesel liquids be used as a blending stock for middle distillate ground transportation fuels by the military. The U. S. Navy is considering allowing up to 20% biodiesel to be added as a blending stock to petroleum diesel fuels. It is important for operational consideration to look at the many problems this could present. Among the more important considerations are storage stability, filterability, fuel compatibility, oxidative stability, and induced instability reactions.