I've seen a couple mentions of the Techroline product from Chevron. I used to have my Hondas serviced at an independent Honda only shop and they recommended it after I complained about an idle that wandered on the tach. They said it was a good product even though in general they did not believe in the "mechanic in a can" concept. I called Chevron tech support to ask about their two similar products and was told the Techron Concentrate Plus is a better product than the Pro Gard. I run one bottle thru with each oil change on my Odyssey but haven't decided yet if I am going to on the Prius.
As far as I know, you don't have to add techron if you regularly fill up with Chevron. My understanding is that top tier gasonline (of which Chevron is one) already have all the detergents you need so no need to use additives if you use top tier gasoline.
Perhaps a domain expert can correct my understanding, but isn't this a bit like paying for "green electricity?" All of the electrons come through the same wires, and even the same substations, but a certain amount is generated by green sources--wind, geothermal, etc. So, if I pay 10 percent more for green electricity, one might argue that since everyone on my street gets their power through the same wires, what's the point in going green? But in the larger picture, I'm supporting the construction of windmills, and so forth. If I pay Shell for fuel, aren't I supporting construction of oil wells in Nigeria? I think so.
A friend of mine who works as a tire engineer for Honda swears that the "Techron" in Chevron gas is actually not a gimmick, and it's what they use on all their long test runs.
I try to buy Sunoco as they advertise, NO ETHENOL, in this area. Even if the price per gallon is a few cents more, the mpg make up for it. PS: My Model-A burns anything, they were made for that.
I don't specifically select a brand, but I mostly commute with my car, about 30 miles per day, on the same route, so I know what's available. The cheapest stations are invariably the Esso/Tesco Express outside my house, and the BP just across the river, which are normally the same price. I therefore use BP because it's not Esso. I could travel a little further to a full-size Tesco supermarket but I did notice worse power from their fuel the last time I used it, though that could be psychological rather than measurable. I don't think the minor cost saving warrants the extra travel and inconvenience to fill up there.
Sunoco almost exclusively. Had a Grand Prix that would stall at lights every time I used BP. There are also 3 of them on the same road along my 4.2mi commute to work.