If the price goes up and you have gas in your tanks why do you raise prices?

This is a normal market function. Remember that the reverse happens when the street prices go down. In an ideal situation all of us including (motorists and retailers) would like a full tank when the price goes up and empty tank when the prices go down. Obviously an empty tank is not desirable when either driving a car or when selling gasoline, so we are often caught in the reverse situation with plenty of fuel in our tanks and we must reduce prices to meet competition.