It has been proposed that renewable energy sources be substituted or at least used as blending stocks for middle distillate ground transportation fuels. The U.S. Navy is considering allowing up to 20% soybean biodiesel to be added as a blending stock to petroleum diesel fuels. It is important for operational considerations to look at the many positives and/or negatives that this could engender. Among the more important considerations are storage stability, filterability, fuel solubility, oxidative stability, and induced instability reactions. This paper reports on methylated recycled restaurant soybean cooking oils used as blending stocks for ground transportation diesel fuels. We compare this recycled soy liquid in blends of both 10% and 20% with petroleum middle distillate fuels for storage stability, oxidative stability, solubility, and chemical instability results. These results are contrasted to those of pure soy-derived fuel liquids used as blending stocks.