Focusing on a RON98-E0 surrogate model, the dependence of the mixture reactivity on equivalence ratio and temperature is obtained by its autoignition delay map reported in Fig. 1, as computed from a constant pressure reactor. The end-gas thermo-physical range is highlighted in Fig. 1, and it is comprised between 700K and 900K, from slightly lean to quite rich mixtures (Ф from 0.9 to 1.4, as a first estimate). This visual assessment is useful to gain a first-glance sensitivity of the gasoline model to temperature and mixture variations, both of which can be locally relevant in the investigated GDI engine. As expected, a strong dependence on temperature is verified for all the equivalence ratios. However, for mixtures close to stoichiometry and slightly lean a non-negligible reactivity dependence emerges also on local equivalence ratios. Hence, a detailed description of fuel mixing in the periphery is fundamental in order to retrieve an accurate estimation of the ignition delay.