Although studies have shown benefits in both emissions and fuel renewability for hydrogen fuelled vehicles, implementation of such a vehicle has been slow due, in part, to a limited hydrogen infrastructure. This situation, along with the proven benefits associated with natural gas and natural gas/hydrogen fuelled vehicles resulted in the need to develop a vehicle capable of operating on any blend of natural gas/hydrogen, at anytime. Such a vehicle dubbed; Variable Gaseous Fuel (VGF) vehicle, in principle, could use a thermal conductivity sensing device developed at the University of California, Riverside, College of Engineering - Center for Environmental Research and Technology (CE-CERT) to directly measure the composition of a natural gas/hydrogen blend. The resulting electrical signal from this device can, in turn, be used as an input to “multiple map” engine control module to control fuel injection and ignition timing. This fuel sensor is simple in principle, promises to be inexpensive to produce (in quantity) and reliable in operation.