IrishEyes, refer to your owners manual and it should very clearly spec which octane the engineers intended for your car.
Gas prices in my travels (Weirs Beach to Franklin through Tilton, Belmont, Laconia) shows me that usually Exit 20 gas stations are the cheapest, but occasionally either Franklins or Laconias will be lower.
Last week in North Anodover, MA, gas was about $0.10 / gallon lower then up here.
Remember to drive fast and take chances!