I have an uncle who owns a Shell Gas station in Alpharetta, GA and he tells me that the same tanker that fills his tanks of gas, fills the tank at a competitor 2 miles down the road. I don't know about other states but in Georgia it is common business to communicate with the competitors and have an understanding that for that day the prices will be a certain amount so they don't get into a price war. Atleast that is how he explained it and how he knows that the same tanker fills most other gas stations. The only exception according to him is Exxon Mobil because they have their own fleet of car and are dedicated to only Mobil Stations.