Fuel prices and oil prices is speculation?

We just got an interesting chart produced by Prezzibenzina. com. As you may have guessed the theme is that the price of oil than gasoline at the pump. It 'widely believed that when the price of oil rises, pump prices of petrol and diesel go up immediately. The same thing would not occur in reverse: prices of oil and fuel do not decrease as fast. Some consumer groups say it is true, the oil