SUMMARYThe resistance of fluoroelastomers to methanol containing fuels has been assessed using standard test methods. The fluorine range covered is 65 - 70 %F. Tests were performed at various temperature, in the range 23° to 115°C. The data obtained demonstrate the better fuel resistance of high fluorine FKMs but one of the most important aspects of this work is the consideration of the non-equilibrium conditions of standard test methods. Therefore specific tests were made to study the kinetic aspects of swelling and a method was developed to assess the permeation rate of methanol through FKM membranes.