Hi Oli,
Ref your statement above: The plastic push-to-connect fittings most people and manufacturers use ( QStype Festos fittings) are not designed to be used with fuels.
All of the turbines I have ever owned have festo fittings for fuel input. Is this a problem over time on the engines themselves? I have never had an issue but am surprised the turbine mfg. use them based on your statement.
Gary