[1fastdog]

In regards to gasoline quality? Most brands are merely additive packages as the base fuel is taken from the same storage tank as any one else's most of the time and in most places.

Sometimes fuel brands hit the additive correctly and sometimes they miss. Sometimes it's a region by region issue.

Where it's allowed, ethanol percentage can whack the optimum AFR on a brand by brand basis. When gas is cheaper, the ethanol percentage usually falls under the "legal" limits allowed but when gas gets high enough, it's a Forrest Gump box of Choc'lets deal.. Ethanol is not big on MPG, but if you can reliably tune for a fixed amount, you can roll with the octane boost. Unfortunately, it's a moving target where allowed.