The method proposed here, allows estimation of the fuel tendency to produce ORI. The procedure lasts 32 hours and is carried out on a dedicated CFR-engine. The ORI is evaluated by comparison of the KLSA (Knock Limited Spark Advance) level, between the beginning and the end of the procedure.In order to optimize the engine parameters, their influences on the ORI were investigated. Particularly, the impact of four of them fuel/air equivalence ratio, coolant temperature, spark advance, load) was precisely quantified, using an experimental design method.Combustion parameters were also followed during the tests. It was observed that the heat transfer modifications contribute greatly to the ORI. Thermal diffusivities measured on the piston-top indicated that deposits located on here are not the main source of ORI.