I came across this post:
"Any way to aggregate MPG by gas attributes?
IE group MPG by different gas stations, fuel type, location, etc, across the same type of car in the same region."
But it was too old to comment on.
I'd also be interested in this data. People claim all sorts of things about how gas stations differ, and it would be great to see some hard data covering the difference in average mpg by gas station brand (grouped by state or month to minimize confounding variables), or how mpg differs by gas station brand for the same car, aggregated.
So, I just wanted to see if there have been/will be any exciting updates of how Fuelly is analyzing this data, now that it's been collected for 6+ months.