No mention but it is the fuel of choice for microlites, it could account for the higher than expected fuel burn.
And who's to say that it wasn't carb icing that stopped the donk. Long decent from FL100 power up to fly level to the castle cough, splutter, fart bobs you uncle.
What engine is fitted to these things?
Do they have the ability to lean?
Do they even have a carb heat?