I'm sitting in my car now waiting to meet someone for lunch, and I was thinking about the different brands of gas you can fill your car up with. Over in California here, you have many choices of gas stations to pick from: Arco, 76, Shell, Chevron, Exxon/M...
Arco is know to car enthusiasts as really bad grade of gasoline. I recall that in the past the Porsche forum guys had a technical post about the different gas available in Southern California. Costco if there is one close by is inexpensive and good gasoli...
and found that I pretty much get the same mileage no matter which I use. As for the performance, I purposely used the various brands to see if there would be any change in performance but I didn't notice any. I need to use the premium, higher octane. But ...
If your car has a knock sensor, it will compensate for the lower octane rating by modifying the ignition curve - basically retarding the ignition a little. This may account for the worse consumption (as well as the lack of 'zing' that Anthony notes)