All gasoline made in the United States has to meet a minimum formula composition per FEDERAL guidelines. This means all cars can run on the same gasoline. All gas is the same. Just so I'm clear...ALL GAS IS THE SAME because the feds say so!
So, it doesn't matter which refinery is making the fuel, they all make it the same...which is why x refinery is making fuel for MULTIPLE gas companies.
The difference is what's added to the fuel AFTER is made. For example; when I worked at the Arco distribution depot as a heavy diesel mechanic I would see Arco trucks, 7-Eleven trucks, Costco trucks, Ma and Pa trucks all come get gas at the same tanker fueling stations. The only difference was the ADDITIVES being added during the tanker fueling operation. There were hoses attached to the main header that would inject the additives as it was being added to the tanker. Think of it as the all-in-one soda machine that all injects the same soda water, but injects the syrup for Coke, Diet Coke, Dr. Pepper, etc.
Some oil companies have better additives than others. Chevron is the best, period. Mobil and Shell have their special chemicals too. As an example of Chevron being the best fuel, you can't buy Chevron in Detroit. But the automakers have Chevron fuel trucked in to Detroit for all their automotive engine certification runs because its the best and cleanest. Its why I only run Chevron gas in all my vehicles.
While Chevron already includes "Techroline" in their fuel, you can buy "Techron" at the automotive stores and add it to your tank. Does it work? Absolutely. After every tune-up I'd add a bottle of Techron to my customers car and tell them not to refill the tank until it was almost empty (per Chevron's instructions). This served to NOT dilute the concentrated fuel mixture so it can go to work on the fuel system. One bottle would do it and made a noticeable difference.
Back in 1985 I rebuilt a carburetor for my 1975 El Camino. When I removed the carb I noticed how dark the intake runners were in the manifold. I didn't get the float level set correctly and after a week of running the new carb I removed it to fix the float level. The intake runners were CLEAN this time! I had run a tank of Chevron fuel and one bottle of Techron when I originally installed the carb the week before. I've also worked on engines of customers who ran Chevron and their valves were clean and combustion chambers were clean. Back in the 80's we were doing a lot of head rebuilds because they had gotten rid of leaded gasoline and the "new" unleaded fuel required hardened seats in the heads. We could tell who ran Pennzoil too! Stay away from Pennzoil!
So buy Chevron's Techron and stay away from the other stuff. Techron works.