Originally Posted by 60wag
What's odd though is that from 4% EtOH on up to 20%, the vapor pressure doesn't change much. So the change from 10% to 15% shouldn't make much difference other than the loss of energy density (lower mpg).
I also thought that was interesting. Makes sense too.
Higher EtOH % will eventually start to be more corrosive on fuel systems not designed for it though.