Plug flow reactors, simulating engine exhaust gas, are widely used in emissions control research to gain insight into the reaction mechanisms and engineering aspects that controls activity, selectivity, and durability of catalyst components. The choice of relevant hydrocarbon (HC) species is one of the most challenging factor in such laboratory studies, given the variety of compositions that can be encountered in different application scenarios. Furthermore, this challenge is amplified by the experimental difficulties related to introducing heavier and multi-component HCs and analyzing the reaction products. In a continued effort to minimize the differences between the synthetic and real engine exhaust gas conditions, we equipped a flow reactor system with an in-house designed diesel fuel injection capability that allowed us to quantitatively reproduce some of the critical features in the HC and NO oxidation processes, observed in real-world operation of Diesel Oxidation Catalyst (DOC). In this article, we demonstrate the usefulness of this capability for capturing the impact of HC species, HC concentration, and NO concentration on DOC performance, including various inhibition and extinction behaviors.