Petrol Price Dropped. Why isn't the food price?

I were pumping my car petrol when the pump stops at a lower cost than the usual one I seen. I thought the pump faulty, thus i try pump once again. But still pump stop again. Then only i remember the petrol rate has dropped few days back.
Wow.. feeling amazing as this time the differences is quite big. 👍👍
But then, suddenly something comes up to my mind. Always when the petrol rate increased, most food or drink price too increased. This time the petrol rate drop a lot. But i don't see that the food or drinks I paid get cheaper also. It remain on same price..
Seriously??? To be honest, I can't believe and accept it. Is this what we called fair?  Hmm..