Placebo? Certainly possible. Bigger difference in the way a station handles fuel than in what kind of fuel is also certainly possible as well as water in the mix. High volume stations are what I look for also. I also do not fuel when a tanker truck is refueling the stations tank. That process has to be disrupting the sediment on the bottom of the tank and putting into the pumps. Dispelling the myth of more expensive high octane gas is better gas is a tough one to squash. The labeling has some to do with it I think, with the regular vers premium thing. Google or Bing octane and you can read a ton of stuff with almost everyone agreeing no benefit to hi-test if your engine does not need it.