A Catalytic Hot Wire Probe (CHWP) technique has been developed to estimate local fuel concentration near the spark plug of a 4-valves Spark Ignition Engine. Various levels of gasoline concentrations, stratification and tumble levels have been achieved by modifying the injection and intake valve configurations. To validate this CHWP technique, local fuel concentration was also measured by using an optical diagnostic technique: Planar Laser Fluorescence (PLIF). Comparative results show good agreements, capabilities as well as limitations of both techniques. It can be concluded that CHWP is a minimised intrusive, inexpensive and easy technique which allows the evaluation of cylinder mixture preparation near the spark of an SI engine. This is a promising technique which could be used, in the future, to evaluate the mixture stratification in direct injection engines.