Bad gas is such a rarity that the only thing I do is avoid some off the wall gas and grocery store in the middle of no where.
If you follow a fuel truck from a refinery you will see it stop at several different brands . The only real difference is the additives they put in with the fuel.
Edit : A simple Google search would have answered the question for Clueless . The Phillips 66 site will show that they actually have more additives than required by the EPA and more than needed for a Top Tier rating.