We present an investigation on the chemical influence of some exhaust gas recirculation (EGR) compounds on fuel oxidation, especially the effects of NO and ethylene. Two experimental setups were used: a homogeneous charge compression ignition (HCCI) engine and a jet-stirred reactor (JSR). The first one was chosen for its representativeness and the second one for its well-controlled operating conditions. NO and ethylene were selected because NO is known for its high reactivity and ethylene has a high concentration in the EGR gases. A complex impact of NO and little influence of C2H4 on the fuel oxidation kinetics were observed, in accordance with the literature. However, a synergistic effect on fuel oxidation was observed by coupling between NO and ethylene chemistry. For the fuel oxidation, a considerable inhibition at low temperatures and a significant promotion at higher temperatures were observed. These results tend to demonstrate the importance of taking into account the complexity of EGR composition.