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An experimental study on the performance and exhaust emissions of a spark ignition engine fueled with methane(CH4)- hydrogen (H2) blends was carried out at a constant speed of 1500 rpm and fixed excess air ratio (λ) of 1.5. The tests were carried out for pure methane and 2 blends (H2, 7% (by vol) of H2, 23% (by vol) of H2) at part load conditions in a naturally aspirated, three cylinder engine with a compression ratio of 9.3:1. The effects of hydrogen addition was studied at various spark timing and it is observed that the Maximum Brake Torque timing (MBT) retarded with increase in concentration of hydrogen. The coefficient of variation in indicated mean effective pressure (COV imep) decreases in blends, indicating stable combustion with hydrogen enrichment. A decrease in burn duration is observed and the crank angle at which peak pressure occurred, is tending towards top dead center (TDC) with increase in concentration of hydrogen due to higher laminar flame speed of the mixture enriched with hydrogen. In case of blends, specific emissions of carbon monoxide (CO) and unburned hydrocarbons (HC) decreases. However, there is considerable increase in specific emissions of oxides of nitrogen (NOx).