I am by no means an expert but as it's explained in the book
Oil on the Brain all gas is the same. Retailers all get it from the same refinery (in a given area). The book explains that trucks from Mobil, BP, Shell, and the distributors who serve the independent stations all get their gas from literally the same pipe at a refinery. They can and often do put additives (like Top Tier) in after they get it but the actual gasoline is all the same....