The benefits of SOFCs are likely to be optimally realised using fuels other than pure hydrogen, which is best employed in PEMFCs. This paper examines a number of plausible fuels including pure alkanes such as methane and iso-octane, Other compounds such as ammonia, methanol and methanoic acid have been shown to react very cleanly when injected directly into the SOFC. More complex fuels, e.g. ethanol and ethanoic acid tend to produce carbon deposits unless the inlet stream is much diluted, e.g. with argon or carbon dioxide. More complex real fuels such as natural gas, landfill gas and gasoline are also mentioned. The experiments involved mixing the fuel with a carrier gas and passing the composition down a zirconia fuel cell tube to examine electrochemical output, while analysing the reaction products using mass spectroscopy. Any carbon deposited was measured by temperature programmed oxidation at the end of the experiment. Windows of operation were found for many of the fuels examined.