The paper describes an experimental research which addressed the study of a 4-cylinder, spark-ignited, port-fuel-injected, production engine modified for hydrogen-methane blend fueling. The original engine was a 2.8-liter, naturally aspirated, methane-fuelled engine. The engine modifications included two fuel injectors per port and ECU replacement for controlling lean burn combustion and enabling real-time variation of the fuel blend, based on an alpha-N mapping approach.Since hydrogen infrastructures are an issue and its production costs are still today very high, pure hydrogen usage is not a viable solution for near future vehicles. In view of this, in the present paper, the maximum volumetric concentration of hydrogen in methane has been set to 35% (which on a mass basis corresponds to 6.3%).The variability of the fuel mixture has been achieved by installing two separate fuel lines connected to two fuel rails: a total of 8 injectors are installed. Four injectors deliver pure methane and the other set delivers a mix of 35% H₂ - rest methane (by vol.). By controlling the injection duration of each injectors group any content of H₂ in methane from 0% up to 35% can be achieved. In this context the aim of the work is the assessment of the potential of this variable fuel feeding depending on the demand, at various speeds and loads.The study points out that a good improvement in engine thermal efficiency can be achieved using the H₂-35 strategy compared to the baseline methane engine. Also benefits on NOx production are achieved at low load engine points. Modifications required to mechanical components and to the ECU calibration are of minor impact on the powertrain, thus could be practicable for vehicle applications.The study presents the optimization of the combustion through adjustment of spark timing and injected fuel quantity at selected engine points. Afterwards, the application of the combustion strategy for the engine calibration is shown.