This study examines the impacts of equivalence ratio and temperature for different liquid–gas fuel mixtures such as hydrogen, methane, propane and benzene, ethanol, gasoline, hexane, isooctane, methanol and toluene on the variation of power output, thermal efficiency, efficiency of exergy (second law efficiency) and NO formation were examined. The mixtures consist of 50% of liquid fuels and 50% of gaseous fuels. The results revealed that the equivalence ratios and fuel temperatures remarkably affect the NO and performance of the spark ignition engine. The minimum values of performance characteristics of the fuels are attained at 1.5 of equivalence ratio. Maximum power output values are observed at 1 of the equivalence ratio. Power, thermal and exergy efficiencies decrease with increasing fuel temperatures. However, NO formation has reverse relation with temperature. Maximum and minimum values of power output are 16.21 kW and 1.03 kW which are observed with toluene–hydrogen and methanol–hydrogen mixtures. Maximum and minimum values of thermal efficiency are 45.04% and 3.29% which are observed with benzene–hydrogen and methanol–hydrogen mixture combustion. The same mixture kinds provided maximum and minimum values of exergy efficiency and NO formation as 45.24–3.28% and 1.83E-06 mol/cm3–2.97E-32 mol/cm3, respectively. In the results, the performance characteristics are changed depending on equivalence ratios and fuel temperatures.