I believe it is 104 a local station here sells it, but never investigated it. But the post below about reg fuel boiling at 140 has me wondering if maybe mixing in 5 gal of race fuel to a tank would help with vapor lock. I do plan on fixing the problem this winter, this will be a bandaid fix for the summer.

point.Summer blend for Denver is EPA mandated at 7.8,what that equates to in boiling degrees I do not know.For $37.00 you can get 10 pages of formulas and have at ithttp://www.astm.org/Standards/D323.htm