A new hydroprocessed renewable diesel (HRD) fuel comprised both straight chain and branched alkane fuel components. In an effort to find a research surrogate for this fuel, single cylinder engine testing was performed with various blends of n-hexadecane (cetane) and isocetane in order to find a binary surrogate mixture with similar performance characteristics to that of the HRD. A blend of approximately two-thirds n-hexadecane with one-third isocetane showed the most similar behavior based on conventional combustion metrics. Companion combustion modeling was then pursued using a combined detailed chemical kinetic mechanism for both n-hexadecane and isocetane. These modeling results show both the importance of isocetane in lengthening ignition delay (IGD), as well as the overall importance of chemical ignition delay as the dominating effect in the overall ignition delay of these binary blend fuels.