In an effort towards predicting the combustion behavior of a new fuel in a conventional diesel engine, Hydrotreated Renewable Jet (HRJ) fuel was first run in a military diesel engine across the entire speed-load operating range. Ignition delay was characterized for this fuel at each operating condition. Next, a HRJ surrogate fuel was developed in order to predict the combustion performance of this new renewable fuel. A chemical ignition delay was then predicted across the speed-load range using a detailed chemical kinetic mechanism model based on an 8-component surrogate representative of HRJ. The modeling suggests that rich fuel-air parcels developed from the diesel spray are the first to ignite. The chemical ignition delay results also show decreasing ignition delays with increasing engine load and speed just as shown by the empirical data. A moderate difference between the total and chemical ignition delays was then characterized as a physical delay period which scales inversely with engine speed. The approach used in this study suggests that the ignition delay and thus start of combustion may be predicted with reasonable accuracy allowing for the analytical assessment of the acceptability of a new fuel in a conventional engine.