Multi-gaseous fuel composition internal combustion

The present disclosure discloses an internal combustion engine system 101 fueled by a multi-gaseous fuel composition, a gaseous-fuel delivery system 105 and the method of obtaining a user-defined 112 composition of plurality of gaseous fuels. The internal combustion engine system 101 comprising an internal combustion engine 102, an intake manifold 103, an exhaust manifold 104, a gaseous fuel delivery system 105 is configured to operate the internal combustion engine 102 using a user-defined 112 composition of plurality of gaseous fuels, and further to vary compression ratio, equivalence ratio, air-fuel ratio and ignition timing based on instantaneous speed and instantaneous load, in order to enhance brake thermal efficiency of the internal combustion engine 102.