On 09/02/2011 07:00 AM, Bill Schertz wrote:

Actually, if you just mix ethanol with gasoline, the vapor pressure will go up (not like salt in water). To compensate, the refiners formulate the gasoline that is going to be mixed with ethanol to have a ‘lower’ vapor pressure (volatility) so that when the ethanol is added the vapor pressure is then in the right range.

And for 91 octane, they make the vapor pressure higher than for 87.  How else would they hold back detonation.

BTW, beautiful work, Steve.  Basically, it boils down to (haha, see what I did there) the fact that most people should be more concerned with melting their cowl off than boiling fuel in the line.