The change of the fuel to a bio-fuel in a gas turbine combustor is a defiant challenge due to there is not enough information about the thermal behavior into the combustor, even there is not information about the change of conventional fuel used. In these sense, a numerical analysis using Natural Gas, Diesel and Bio-Ethanol is presented. The results show a significant reduction of the Turbine Inlet Temperature (TIT) when the diesel and bio-ethanol are used in the gas turbine combustor (TITNatural Gas = 1,262.24 K, TITDiesel = 1,204.67 K and TITBio-ethanol = 918.24 K). This leads to an increment of the diesel and bio-fuel mass flow rate in order to reach the allowable condition of the gas turbine combustor. As it is well known, the reduction of the TIT means a reduction of the output power of the gas turbine, thus to avoid this, the increase of bio-ethanol was about 255.5% and diesel was about 112.2% (considering 3.6 kg/s of fuel as the full load). This paper gives an attempt to discover the viability to use bio-fuels in gas turbines from the thermal-fluid dynamic standpoint.Copyright © 2012 by ASME