Does the BP gas that I use at a particular station give me significantly better mpgs? That's my hypothesis.

Background: About 2 months ago, something happened when I filled up at my favorite BP gas station near my house. Where I normally get 64-65 mpgs on the dash readout in the summer, suddenly I was seeing 70. Sure enough, after finishing the tank, I went 859 miles for 64.8 calculated mpgs. The next tank was very similar -- 865 miles for 64.3 calculated mpgs. Those two tanks are the highest I've recorded in the 2 years I've owned the car, and by 4 mpgs at least.
The weather has been the same, I'm driving the same route back and forth to work, nothing has changed.

So, I decided on my last tank to fill up at Marathon. Yesterday I finished the tank -- 764 miles at 58.5 calculated mpgs, which is what I *used* to get in the summer before these last 2 BP tanks.

I filled up at my favorite BP again last night. Then a really peculiar thing happened on the flat road out of BP back to my house. I was driving steadily along, about .3 miles from BP, at 60 mpgs on the FCD, when all of the sudden I felt a surge. I had to back off on the gas to maintain speed (the surge was accelerating the car), and once I got it steady, was at 100 mpgs on the FCD.

So this morning, I drove my regular 13.2 mile route to work, and when I got here....84.7 mpg on the dash, back up to what I'd expect from the previous 2 BP tanks.

Was I imagining things? I wasn't expecting this "surge", so my gut feeling was I burned all the old gas out of the fuel line, and the BP gas mixture hit when I felt the surge. Now, this surge wasn't like Nitrous or anything...but you could feel it. What do you think?

It takes a while to test this theory, as I have to go through a whole tank of gas to do it, but my preliminary findings say, there's something in that BP gas.

Mark