[WardL]

Most of pump gas across the country is supplied by fungible fuels. The refineries make 87 and 91, 92 or 93 octane gasoline. It is supplied to the market place to minimize cost and supply disruptions. You could buy brand A supplied by refinery A and later go to the same station and buy brand A gas supplied by refinery B gasoline. It will typically be at the octane supplied. There are unique areas of the country where a brand is normally supplied by one specific refinery separate from the other brands in the same area.

Yes, all gas is the same until the proprietary additive is mixed into the tanker truck. The EPA requires a minimum dose of additive to keep the engine clean. The majors typically have enhanced additive packages that keep your engine cleaner than the EPA requires.

Typically the state controls the amount of ethanol and if the pump has to be labeled with percent ethanol. Almost all the fuel on the West Coast has 10% ethanol. Of course California has clean burning CARB gasoline. Phoenix has emission controlled gasoline.

There are many formulations for race fuel. Each fuel is suited for a particular engine. Carborated engines with no computers have completely different needs than the latest ALMS racing engine. A blender will make up several different formulations send them to the race team and they will choose the best formulation for their engine with bench testing.