Laser-optical investigations in IC engines often rely on fluorescing tracer-substances which are added to the fuel. In particular, several aromatic substances (like alkylated benzenes or anisole) are popular candidates for the purpose. In many applications, the question appears to which extent the addition of tracers affects the auto-ignition and flame propagation during engine operation. Compared to a pure fuel/air mixture, the tracer addition may not only influence the chemical properties, but also the physical properties. In practice, both aspects can be relevant for engine operation, and they may interact due to the dependence of chemical reaction on physical conditions. In this paper, we study the overall influence of selected aromatic substances on engine performance by numerical modeling. The model features a detailed treatment of chemical reactions for both the fuel and the tracers. Different aspects of the engine cycle are modeled. Studies include a variation of engine parameters (speed, compression ratio, equivalence ratio, tracer content), and the dependence of output variables like auto-ignition timings and maximum pressures on these parameters is investigated by performing a large set of parametric simulations. To highlight the difference between physical and chemical influence of the tracer, we compare the case of engine operation with pure fuel/air mixture and with a tracer-fuel/air mixture under different aspects: First, a comparison is made based on equal physical conditions, namely equal temperature, pressure and equivalence ratio. In contrast, a second way of comparison is based on equal engine operation parameters. While the first highlights the kinetic aspect of the tracer-fuel interaction, the latter additionally includes the modification of the physical conditions of the mixture by addition of the tracer.