Assume that some rational consumer X has satisfied the optimal purchase rule (the equi-marginal principle) and then the price of gasoline drops. If everything that X purchases is a normal (superior) good, then....
X will purchase more gasoline and also more of everything else
X will purchase less gasoline and more or less of everything else
X will purchase more gasoline and more or less of everything else
X may purchase more or less gasoline and more or less of everything else.