yes. there is a difference in what is added to gasoline (such as additives like ethanol).
the main component of gasoline is octane (hydrocarbon of 8 the stable part of gasoline)
mixed with heptane (hydrocarbon of 7 that is notoriously unstable and know for detonating under high pressure and troublesome in turbos)
the octane rating at the pump is suppose to be the percent equivalent of the amount of octane (but not the actual amount). the best places to get gas in California as far as quality are from shell, chevron, and 76.