From a barrel of purchased oil to the gas station is a trip involving lots of intermediate steps and I imagine some degree of time. I would also think the producers, distributors and vendors (ie stations) have fixed invested costs in the gas. Why are fluctuations in the price of oil reflected almost instantly in gas prices?
If gas drops 40 cents in a week isn’t the gas station owner potentially losing money with every tankful he sells if he bought it when gas was 40 cents higher? Why the virtually instant response in end user prices when the barrel-head commodity price rises or drops?