Abstract : Fuel System Icing Inhibitor (FSII) is composed of DiEthylene Glycol Monomethyl Ether (DiEGME). FSII provides fuel system icing and microbial growth protection to aviation fuel systems. The current FSII specification requirement for JP-5 aviation fuel is 0.10-0.15% by volume. The lower use limit for naval aircraft per NAVAIR 00-80T-109 is 0.03% by volume. The goals of this study were to determine if the current specification requirement could be decreased while still providing satisfactory icing and microbial growth protection. A parallel effort was to determine what cost savings could be realized if the injection rate was able to be effectively lowered. Therefore a cost benefit analysis was performed on different injection ranges.