YVR is correct. The entire reason that gasoline is sold at lower octanes has more to do with elevation than anything else. The gasoline pool(s) established by local refiners are specifically established at a certain octane level. Refiners would rather keep the octane as low as possible as it allows them to make other feedstocks or hold high octane products in reserve to ship to other markets or for when they run a less agreeable crude slate to make gasoline. Refiners try not to put gasoline into the pool that has a higher octane value than required as it is a higher value product.

The Northeast is different from other areas of the country due to having large populations at sea level and significant populations above 2000' elevation. This allows more pools to be created that gas stations may purchase from without increased transportation costs due to the storage locations being closer than in other areas of the country. Of course, lower octane gasolines cost less but I would be more concerned about the gas station owner charging market price for 87 Octane and actually selling 85. Yes, this is illegal but only if he/she does not change the sticker on the pump to the 85 octane.

As to performance in an automobile, YVR is correct again. Basically, unless your vehicle stipulates the use of high octane fuels, buy the cheap stuff provided that the station owner is reputable. There were station owners that were selling PERC, or dry cleaning fluid, blended in their gasoline. As this is a chlorinated benzene molecule, this is bad news all around. Engines ceaze or throw rods, corrosion everywhere and who knows what a catalytic converter will put out. Chlorinated benzenes are not supposed to be in gasoline so either the gas station owner is selling PERC blends or the refinery has a major quality control issue.