Stay right the heck away from Seven-Elevens...
That has to be the worst gas in the country...
I think you would get better gas mileage if you poured their beer in your tank...
My TOAD gets a pretty even 25 MPG with any other 87 octane gas and on average... 19 - 21 mpg with 7/11 gas... (had to get it a couple of times on the way home from work...
My former employer had a bulk contract with them, at one point... My inspection vehicle (Ford Explorer) got around 6 MPG (it would sit and idle a lot..) When we switched contracts to Mobil... 11 MPG for the same duty...
Oh yeah and I am convinced that SeaFoam in the tank helps fight the effects of Ethanol... I use a 16 Oz. can in full tank of regular gas (80 gal.) and picked up about 1 - 2 mpg... (between 6 - 8 without... and 7 - 10 with...) BTW: the 10 mpg was on a flat calm day at 45 - 60 MPH for over 2 hours and 150 miles with no stopping or following traffic... (The Treasure and Space Coast section of highway A1A, in Florida... Highly unusual...!
I have also started using Lucas synthetic oil treatment after each oil change too... (manufacturer states you can mix synth with dino oil to fortify the oil and add protection from dry starts...) Ford V-10 does not recommend synthetic in engines that are going to sit for any legth of time... (like motorhomes) because synthetic is so viscous... it will try to seep out from anywhere... even where seals are normally good...