I am very lucky to have a station near me that sells ONLY non ethanol regular gas. I tried a tank and got very little change in MPG. I have worked my refuel schedule so I can fill up there every time. I am now on my 3rd tank and I am getting much better MPG. I filled up Friday, worked all weekend putting 228 Mi on the hatch and I filled up/topped off this morning with 5.5 gl. that is 41.45 MPG. My last MPG check was 36.8 MPG so that is an improvment of 4.65 MPG
Note on my driving-35 mi one way to work 30 mi on highway at 70 MPH for about 350 mi per week. I have 8k+ on the car now over about 5 months.