A synthetic fuel formula using a blend of High Density Synthetic (HDS) (e.g. Decalin and Tetralin), and Low Density Synthetic (LDS) (e.g. Synthetic Paraffinic Kerosene—SPK) is disclosed. This HDS and LDS blend has been shown to be useful as a jet, rocket and diesel fuel of standard density, and under low temperature conditions. The inventions described herein relate to 100% synthetic hydrocarbon fuels derived from various carbonaceous materials such as, but not limited to, biomass, municipal waste, natural gas, and coal. This 100% synthetic fuel can be universally used for both jet and diesel fuels. It meets Joint Battlefield Use Fuel of the Future (J-BUFF), or Single Battlefield Fuel (SBF) strategic requirements. The commercial advantage of the present invention is that it can be prepared from commercial available fuel stocks or co-processed using currently available chemical processes.