No one's being an asshole (yetI don't mean to be an asshole, but I fail to see what the myth is. I also fail to see why I should stop paying 4 cents more per gallon @ Sunoco vs GE or Shell when I have proven to get between 30 and 50 more miles per tank. 30 to 50 miles for 64 cents a week (per tank) seems worth it to me, unless I'm missing something.

The myth is gas from any of the major brands being significantly different from one another. Yeah, they all have their own "proprietary" additives but the actual gasoline/ethanol mixture is the same. Another thing I've noticed is that if I expect to get worse fuel economy I do. That is, the perceived "benefit" of using one brand of fuel over a nearly identical competitor is likely a placebo. Do you know if Sunoco has a lesser ethanol content than Shell or GE? That would explain the slightly higher price and better fuel economy if it was. I don't know and there aren't any near me so I can't check.