The car handles octane by tweaking based upon the knock sensor and does it right away. The rest of the time the car uses the O_{2} sensor to adjust the mixture and this happens in a fairly quick, 1-10 second cycle. I'm not aware of any mechanism that spans larger time intervals.

As for the gasoline studies, I did regression testing by going back and retested the original brands weeks and half a year later. I found the same differences showed up. However, I'm not about to claim my results apply in other parts of the country. All I can trust is my data in Huntsville Alabama.

Bob Wilson