Just about every major brand gasoline producer, in particular those that are "certified top tier," has a proprietary blend of additives that get mixed in with the gas sold at their gas stations.
FWIW when I had a Subaru that recommended at least 91 octane gas I found that it ran best on Shell premium gas and the higher the octane the better.
FWIW when I had a Subaru that recommended at least 91 octane gas I found that it ran best on Shell premium gas and the higher the octane the better.