<div class="section abstract"><div class="htmlview paragraph">Although the root-cause of the initial pre-ignition is not yet proven, there is a general agreement throughout the literature that it is very likely a 2-phase particle or droplet induced phenomenon. In the case of a droplet induced mechanism there are still uncertainties regarding the detached droplet size, velocity and composition. Former research work suggests that heavy wall wetting during injection is increasing the PI-frequency in WOT operation points. Due to the oil dilution the viscosity and the surface tension are reduced, which enhances the likelihood of detachment.</div><div class="htmlview paragraph">The present work is therefore investigating the influence of the oil dilution on the droplet evaporation and the PI-tendency. According to previous work performed at the research group, there is an influence of the radical ketohydroperoxide that has its origin in incomplete oil combustion on the pre-ignition probability of an engine cycle. This underlines the role of oil combustion chemistry and the oil mass fraction in detached droplets.</div><div class="htmlview paragraph">In order to characterize the droplet evaporation a multicomponent surrogate model was chosen. The selection of the species is based on the distillation curves and the basic chemical composition using a detailed distillation model. In order to capture mixture effects, the vapor-liquid-equilibrium incorporates activity coefficients calculated by the UNIFAC method. The investigated lubricant oil is modelled as a mixture of four n-alkanes based on a GC-analysis. This established model shows a good agreement with the measurement data.</div><div class="htmlview paragraph">The fluid surrogates are transferred to a CFD-code to predict the evaporation behavior of different oil-fuel mixtures under engine-like conditions. Different release timings during a compression stroke are investigated. The compression is modelled through a time-dependent change of the ambient gas pressure and temperature. Furthermore, a sensitivity analysis of the boundary conditions (D<sub>Drop</sub>, T<sub>Drop</sub>) was performed. It can be shown that a 250 μm droplet can lead to an ignitable condition up to a fuel share of 25 %.</div></div>