I understand that additionally in some vehicles (not necessarily aircraft) predating ethanol dilution the evap systems may begin to malfunction at high elevation and temperature due to the lower initial boiling point of ethanol.
In the case of my vehicle it results in low/rough idle and positive fuel tank pressure which otherwise do not occur either at lower elevation or with ethanol-free fuel at elevation.
In the case of my vehicle it results in low/rough idle and positive fuel tank pressure which otherwise do not occur either at lower elevation or with ethanol-free fuel at elevation.