In this study, the effects of Reactivity Controlled Compression Ignition (RCCI) application on engine combustion, performance and emissions in a diesel generator were investigated. In the experiments, safflower oil derived biodiesel and diesel mixtures were used as the high reactivity fuel (primary fuel) and gasoline as the low reactivity fuel. The RCCI application was provided by the connection of a secondary fuel injection system with the intake manifold. The gasoline RCCI application rate was 30% and 50% of the total mass fuel consumption of the engine and was pre-mixed as port fuel injection (PFI). Tests were performed at a constant engine load (10.8 kW) and engine speed of 1500 rpm. The purpose of using diesel and biodiesel mixtures is to increase the reactivity of the primary fuel that facilitates the start of the combustion. The combustion, performance and emissions, which are the most important parameters of the engine operation, have been thoroughly investigated and the results were presented. In RCCI application, in peak values of pressure, velocity of heat release, average gas temperature partial increases were determined. When the ratio of gasoline PFI was increased, the NOx emissions significantly decreased and the engine efficiency was also increased, while the CO and HC emissions were slightly increased. (C) 2018 Elsevier Ltd. All rights reserved.