Higher octane gasoline is less likely to spontaneously combust under pressure. I live on the east coast and have rarely seen less than 87 octane for sale anywhere. I didn't know it was more common in other parts of the country but it's probably cheaper?

My guess is that 86 is just as good as 87 for most naturally aspirated engines. If you have a high compression engine (turbo or supercharged) you definitely need higher octane.

Has anyone else noticed a difference between different brands of gas? I've never noticed it myself but I have a few friends who swear by certain brands. I always figured they were crazy but maybe it depends on the car.

oops, maybe I should have milked a few more posts out of this