Apparently all gasoline's sold in a given area of the US, with the same octane rating, are the same blends of gasolines. According to the 'American Petroleum Institute' site one of the major costs of producing gasoline in the US today is the need to store, distribute and transport the 57 different blends of gasolines produced in the US, without contaminating one with another. Blends are regulated to comply with the US environmental regulation and those of the various different state regulations. Those regulation, as well a elevation, determine which blend is sold in a particular area. EVERY company selling gasoline in that area must meet the SAME blend specs.
mike hunt