when it comes to gasoline, do brands matter?

Absolutely. The gas that comes straight out of the pipe line is slow death to car engines, and it has nothing to do with octane. Detergents have to be added to make it suitable for modern cars, and although all companies add detergents not all add enough. Toyota, Honda, GM and BMW started the top tier standard several years ago and you can use non-top tier brands at your own risk. A friend at work has a sister who recently had to get her Buick engine rebuilt because of pervasive deposits. I switched to top tier gasoline brands about 5 years ago.

My mother in law is part owner at a chain of gas stations. They use Marathon gas. When they have had their gas tested, it consistently has a slightly higher octane level than what the labels on the pump show. So this is a tough question to answer. If you wanted to know what a gas station really has in their tanks, ask them if they can share their testing information with you. But if they are unwilling, you can still minimize your chances of getting less potent gasoline. NEVER fill your car when the station is receiving a fuel delivery and wait for at least a half an hour afterwards. When the gasoline cascades into the underground storage tank, it stirs up the dirt, sediments, and water trapped inside, increasing your chances of getting some of that in your fuel tank. This advice alone will save you money in the long run, keeping damaging sediments out of your fuel and oil system.

No there is not. Some believe there is, but they're wrong. They are just duped by cleaver advertising. For a time my Uncle Ron drove a gasoline tanker for an independent supplier. He says the raw gasoline all comes from the same storage tanks. The only difference is in what other additives each brand specifies, and for most they are the same, but just called different names. Just buy the cheapest brand that meets your vehicles recommended octane level. (usually 87)

While some may claim yes, personally I've never any difference between any of the major retailers.

The only advice I will give is to not fill up while or shortly after the station has had a fresh delivery of fuel. The freshly added fuel can stir up sediments from the bottom of the underground tank and that may end up in your vehicle's tank (and possibly end up clogging your fuel filter).

yes, they do, problem is, many gas stations are independently owned and so you never know who they are buying gas from, that's why I only buy my gas from large corporations like Quik Trip, they have a reputation to uphold so they usually buy from reliable companies, and since they go through so many gallons a day, the gas is usually fresh. I also look for recently built stations, they will have brand new holding tanks.

If your car isn't running right, try using a higher octane gas (the higher the better too), I never use anything under 91 if I can help it, also, try putting a can of Heat in the tank, especially during the winter months and the beginning of summer when the humidity is the highest, and use the Heat in the red bottle, not the one in the yellow bottle.If you car is fuel injected then use a can of "Seafoam" or "Techron" fuel cleaner, twice a year, that will keep your system clean preventing future maintenance and will give you improved gas mileage

What matters is QUALITY, not brands. Beyond the tiny amount of additives, what matters most is lack of water and particulates in the fuel. I've got junk gas at major stations and great gas at mom and pop places.

I had a SERVICE station years back, All the gas comes out of the same pipe line. some of the additives will destroy you eng.