This is an interesting article about AAA's test of gasoline quality. At the bottom of the article are two links. One that leads you to the TOP Tier website with a list of retailers who sell Top Tier rated gasoline in all grades of their fuel. There is another link that takes you to a lengthily PDF document detailing the methodology use in the test and photographic results showing the difference in deposit build up on intake valves and combustion chambers.
http://abcnews.go.com/US/wireStory/a...oline-40395549
And here is a link to the list of Top-Tier retailers -
http://www.toptiergas.com/retailers/