This thesis considers the role fluids play in improving the efficiency and reducing the environmental impact of modern gas turbines. This includes gas turbines used in aviation, marine propulsion and power generation applications. There are two discrete means of lowering the environmental impact of gas turbines. Improving the thermal efficiency of the gas turbine is one possible route which works by reducing the required fuel consumption. Another route which is indirectly related to engine technology is the use of renewable fuels (biofuels) which have reduced lifecycle carbon dioxide emissions when compared to crude oil derived fuels. As such this thesis examines both the potential of renewable fuels for use in gas turbines and also the impact of increased efficiency on the fluids contained within a gas turbine.