Blending tables for creating E20/E30 in General E85 Discussions Posted July 22, 2008 · Report reply Thanks for the tables, they may be of use to some. Just curious, though - looks like there may be some errors - or I'm reading the tables wrong? For instance - the first row of the first table: 87 Octane (assume no alcohol) = 3.5 gal, mix with 11.5 Gal of E85 to make 15 gal of E20? 11.5 gallons of E85 = 11.5 x .85 gallons of alcohol, or ~9.78 gallons of alcohol, this is the only alcohol in the mix, so 9.78 gal / 15 gal total = ~65%, so E65. But if you flip the table headings, 3.5 Gal of E85 + 11.5 gal or regular ~ E20. Oops! I did goof here by the "flip-flop" method. I did this later on Sunday night and well, I failed to see my error. I can redo this and repost it but...do you want me to post it in this thread or...can this site create a section where we can post stuff like this? I decided to try posting this because I thought it would be easier/quicker to utilize at the pump (if one prints this out and uses it as a reference) then to "calculate" while at the pump. I used a 15 gallon tank because my Escape Hybrid has it. If this "Guide" is handy as a reference at the pump, then should a similar guide be created for 17 gallon tanks or 20 gallon tanks or...? What are the other common size tanks for vehicles? Finally should a reference like this be created for E40?