Even though my Civic is designed to run on regular gas (87 octane), I use premium (91-93) regularly. It just gives me better low-end torque - probably because of the advanced timing, right?
The thing is this (and this was also true for my previous car, a 1993 3.3L Oldsmobile Ciera): I get better mileage total AND per dollar. I.e. more miles per dollar assuming premium is only 20 cents more expensive than regular. And the higher the price of gas goes, the less of an improvement I need to get to justify premium. When gas was back down to $2 it was almost a tossup which one I used.
This is something I encourage everyone to do: Figure out how far a dollar of regular will take you compared to premium. (This of course assumes that there is an actual improvement.)
