Do different Gas Brands burn more efficiently? Higher MPG's?

[cowmeat]

I always get gas for Ron Burgundy at the same Circle K, at the same pump, at the same time in the morning, to the second click of the pump.

I don't know about different gas at different places affecting mpg, but I do try to make sure my tank-to-tank numbers are as legit as possible and reduce the variables as much as possible.

Now in my wife's 2014 Explorer, I'll get gas wherever it's convenient.

[Tulok]

I was a delivery driver for an auto dealership in SoCal for about half a year. I drove the truck and saw it as a perfect chance to test out different gas stations.

I would always do the same sort of routes throughout the week and my tank would last about 3 days. So i kept track of the gas and these are the main points i found:

Every single tank I had that was Chevron or Texaco was the WORST. I can't overstate this enough. every. single. tank. from chevron or texaco. was the worst.

Shell was always the best. every single time. not by a lot, but it was on average 1.5-2mpg better than chevron/texaco.

Really dinky gas stations with no brand name were completely unpredictable. one particular station was almost as bad as chevron/texaco, consistently. Others were right in the middle. but they usually were not up to par with shell.

I couldn't test ARCO or Valero, those ones are supposedly the crappiest, but I can't confirm it or deny it.

This was in a 5.3 Chevy V8 1500 Truck with 88k miles and the AC on full blast at every second of it's life. Averaged between 16.3-18.8mpg in mixed driving.

I saved my MPG sheet somewhere but I can't find it for the life of me.