This paper describes the approach used to improve the fuel flexibility of a high power density diesel engine intended for tactical combat applications. The objective of this work was to demonstrate a technically feasible solution that mitigated the negative performance impacts encountered when commercial and military-grade aviation fuels are used in diesel engines that were calibrated with standard Type 2 diesel fuel. To accomplish this objective, modifications to the engine calibration and the implementation of a fuel compensation algorithm, which used cylinder pressure feedback, resulted in successful demonstration of meeting the program requirements of maintaining acceptable combustion quality and maximum power output to within 2 percent of the rated power target regardless of the fuel type supplied to the engine.