fuel consumtion is worked out with the Specific Fuel Comsumption formula,which is ibs of fuel consumed per hour over thrust(which is the difference between inlet air velocity and thrust nozzle velocity[out let velocity]).The efficency also depends on the compressors ability to compress the air without to much loss in pressure.It also depends on the outside air temp and altitude.The speed of the aircraft so in that it will increase it's RAM EFFECT.Turbine Inlet Temp is also a variable in the engines effiency.The hotter the gas stream the more efficent the engine will become. As a whole jet A1 has a higher calorific value(measured in BTU's,which is about 18,300)than diesel.So the fuel is more efficent in terms of weight and volume. So it's not a simple question of which is more efficent becuase there are many variables in the operation of a gas turbine,in fact there are many more workings that go into figureing out the efficency.But as a whole I would say a Gas Turbine is more efficent,depending on !!!!!!!!!!!!!.Good luck in your quest