A mechanism-derived lumping strategy for modeling the acid-cracking kinetics of hydrocarbon mixtures based on a limited set of pure component experimental data was tested in terms of its ability to predict the kinetics and product spectra from the reaction of a 1-phenyloctane/n-hexadecane mixture. The modeling approach has two main components. First, reactant and product molecules are organized into compound classes, e.g., paraffins, olefins, and aromatics. Second, the elementary steps of the acid cracking of each member of a compound class are constrained by quantitative structure-reactivity relationships (QSRRs) determined from pure component experiments only. This two-dimensional, mechanism-derived lumping approach provided a significant reduction in the number of parameters required to model the cracking reaction. Application of this lumping strategy to the acid cracking of the phenyloctane/hexadecane reacting mixture provided good agreement between experimental data and a kinetic model containing only 14 parameters obtained from separate pure component experiments. The model revealed the applicability of the QSRR-based lumping approach to the cracking kinetics of hydrocarbon mixtures.