More demand in summer, so price tends to creep up in summertime. However, you are correct ... a drop in the price of oil can decrease or even negate the usual summertime increase in gasoline prices. In fact, the recent drop in oil prices has brought down the gasoline prices a little bit, lately.

The essential American soul is hard, isolate, stoic, and a killer. It has never yet melted. ~ D.H. Lawrence