i try to find the balance between price and top tier. searching MSN/gas prices is my guide. i have found ZERO measurable difference in top tier fuels in regard to FE, and what yields what. so, i go w/ the cheapest top tier when it's time to buy.
When I lived in Alaska, there was only one refinery in the state. Obviously it was prohibitively expensive to ship crude down to the lower 48 and to ship refined gasoline back to Alaska, especially with the Alaska pipeline in place.
I watched gasoline tanker trucks leave the Tesoro refinery and deliver gasoline to different branded gas stations from the same truck. I buy the cheapest gasoline, not even top tier.
i have had fuel delivery issues 3 times in my life--speaking to the non-mechanical/quality of fuel variety. all 3 instances were the result of cheap gas, and were corrected when a top tier fuel replaced it.
I've had issues with cheap gas- namely clogged fuel filters. That's the primary reason I stick to name-brand gas that has their own refineries. (I realize that it is possible to get off-brand gas at a name-brand station, but this is usually in remote locations.)
In my summer car (big-block with nitrous), octane rating is crucial. I've had knock buying off-brand high octane fuel, and needless to say knocking doesn't work well with nitrous. Most more modern cars have knock detectors, but I still would rather not have any knock in the first place. Also, higher octane doesn't have the turnover at the cheap gas stations like it does at name brand stations, so it's pretty common to get really old fuel (which isn't good when you need maximum performance).
Some name brands will have their own trucks deliver gas, but not necessarily their own brand of gas in their trucks.
Some names I consider reputable: Shell, Exxon/Mobil, Sunoco. Brands I'll also buy: Irving, Hess, and BP. Brands I won't touch: Citgo, Gulf, Joe's Corner Gas & Hot Dogs.
I won't touch Citgo either, but for political reasons. Another thing to consider is the volume of fuel sold at a location, and how well maintained the station is. High volume means that they will have fresher gas, and if a station is not well maintained they can have problems with water in their tanks. Also, if you see the tanker truck in the parking lot (or pulling out), pass that station by. When fuel is being dumped in the tanks, any sediment and/or water in the tank is stirred up, and can be pumped right into your tank.
Most more modern cars have knock detectors, but I still would rather not have any knock in the first place.
As I understand, knock sensor equipped modern vehicles will always run at the ragged edge of a little bit of knock. They adjust the timing aggressively to find that point...it's not a matter of not having any knock in the first place.