The best gas to use for your car is what the owners manual suggests. In this case regular unleaded is fine. The only change from this if because of mods you get pinging then move up a grade until the ping stops.
In actual fact regular gas has more btu's (or heat) in it that premium. This is because the premium is formulated to vaporize at a higher temperature and compression without preignition burn that is the ping. All grades of gas are formulated for the the season of the year they will be used. Summer regular will vaporize at a higher temp then winter regular. The same with the other grades. So you can stay with the same grade summer or winter.
