It has been proposed that biodiesel liquids be used as blending stocks for middle distillate ground transportation fuels by the Department of Defense. 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 solubility, oxidative stability and induced instability reactions. This article reports on the use of recycled soybean derived fuel liquids. The fuel liquid was derived from recycled restaurant cooking oil with no added antioxidant after reprocessing. We compare this biodiesel in blends of both 10% and 20% with stable and unstable middle distillate fuels for storage stability, oxidative stability, solubility, and chemical instability results.