My truck's mileage seems to vary more on WHERE I buy my gas than the grade of gas. So I'm more worried about the source of the gas and it's refinement/additives. I've tried different stations, but haven't reached a consensus yet. The worst gas mileage I got was from Shell, and the best from Exxon, with Racetrack about midway, all with the same grade.
One thing that concerns me is the age of higher grade gases at the various stations. Regular gas is certainly fresh as it's the highest seller, but how long has that mid-grade (89) been sitting in that storage tank? And does high grade (93) outsell mid-grade? Or maybe the gas is just mixed at the pump, I don't know.
All I know is that my Raptor has a drinking problem, so lately I've been trying ethanol-free at Wawa.